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ltc2974 1 2974fa for more information www.linear.com/ltc2974 temperature (c) ?50 error (%) 50 75 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 ?0.03 ?0.02 ?0.01 2974 ta01b ?25 0 25 100 three typical parts typical application features description 4-channel pmbus power system manager featuring accurate output current measurement the lt c ? 2974 is a 4-channel power system manager used to sequence, trim (servo), margin, supervise, manage faults, provide telemetry and create fault logs. pmbus commands support power supply sequencing, precision point-of-load voltage adjustment and margining. dacs use a proprietary soft-connect algorithm to minimize supply disturbances. supervisory functions include over and under current, voltage and temperature threshold limits for four power supply output channels as well as over and under voltage threshold limits for a single power supply input channel. programmable fault responses can disable the power supplies with optional retry after a fault is detected. faults that disable a power supply can automatically trigger black box eeprom storage of fault status and associated telemetry. an internal 16-bit adc monitors four output voltages, four output currents, four external temperatures, one input voltage and die temperature. output power is also calculated. a programmable watchdog timer moni - tors microprocessor activity for a stalled condition and resets the microprocessor if necessary. a single wire bus synchronizes power supplies across multiple ltc power system management devices. configuration eeprom sup - ports autonomous operation without additional software. 4-channel pmbus power system manager applications n sequence, trim, margin and supervise four power supplies n manage faults, monitor telemetry and create fault logs n pmbus compliant command set n supported by ltpowerplay tm gui n margin or trim supplies to 0.25% accuracy n fast ov/uv supervisors per channel n fast output current supervisors per channel n coordinate sequencing and fault management across multiple chips n automatic fault logging to internal eeprom n operate autonomously without additional software n external temperature and input voltage supervisors n accurate monitoring of four output voltages, four output currents, four external temperatures, input voltage and internal die temperature n i 2 c/smbus serial interface n can be powered from 3.3v, or 4.5v to 15v n available in 64-lead 9mm 9mm qfn package n computers and network servers n industrial test and measurement n high reliability systems n medical imaging n video adc total unadjusted error vs temperature l , lt, ltc, ltm, linear technology, the linear logo, and polyphase are registered trademarks and ltpowerplay is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. protected by u.s. patents including 7382303, 7420359 and 7940091. ltc2974* 4.5v < v ibus < 15v** gnd to p resetb input watchdog timer interrupt *some details omitted for clarity only one of four channels shown **ltc2974 may be powered from 3.3v or 4.5v to 14v v in i ? i + r20 r30 0.1f mmbt3906 r10 2974 ta01 run/ss sgnd v fb bg sw gnd load dc/dc converter v pwr ** auxfaultb ov sda scl alertb control0 faultb1 pmbus interface to/from other devices faultb0 share_clk asel0 asel1 wp v in_sns v dac0 v sensep0 wdi/resetb v sensem0 i sensem0 i sensep0 t sense0 v out_en0 pwrgd v dd33 ** tg
ltc2974 2 2974fa for more information www.linear.com/ltc2974 table of contents features ........................................................... 1 applications ...................................................... 1 typical application .............................................. 1 description ........................................................ 1 absolute maximum ratings .................................... 4 order information ................................................ 4 pin configuration ................................................ 4 electrical characteristics ....................................... 5 pmbus timing diagram ......................................... 9 typical performance characteristics ........................ 10 pin functions .................................................... 13 block diagram ................................................... 15 operation ......................................................... 16 ltc2974 operation overview ......................................... 16 eeprom .................................................................... 17 auxfaultb ................................................................... 17 resetb .......................................................................... 18 pmbus serial digital interface ....................................... 18 pmbus ....................................................................... 18 device address .......................................................... 18 processing commands .............................................. 19 pmbus command summary .................................. 22 summary table .......................................................... 22 data formats ............................................................. 27 pmbus command description ................................ 28 addressing and write protect ........................................ 28 page .......................................................................... 28 write_protect ...................................................... 28 write-protect pin ................................................ 29 mfr_page_ff_mask .............................................. 29 mfr_i2c_base_address ...................................... 29 on/off control, margining and configuration ................ 30 operation ............................................................... 30 on_off_config ....................................................... 31 mfr_config_ltc2974 ............................................ 32 cascade sequence on with time-based sequence off ............................................................ 33 mfr_config2_ltc2974 .......................................... 35 mfr_config3_ltc2974 .......................................... 35 tracking supplies on and off .................................... 37 tracking implementation ........................................... 38 mfr_config_all_ltc2974 .................................... 39 programming user eeprom space ............................... 40 store_user_all and restore_user_all ........ 41 bulk programming the user eeprom space ............ 41 mfr_ee_unlock ..................................................... 41 mfr_ee_erase ....................................................... 42 mfr_ee_data .......................................................... 42 response when part is busy .................................... 43 mfr_ee erase and write programming time ........... 43 input voltage commands and limits ............................. 43 vin_on, vin_off, vin_ov_fault_limit, vin_ov_ warn_limit, vin_uv_warn_limit and vin_uv_fault_limit .............................................. 43 output voltage commands and limits .......................... 44 vout_mode ............................................................. 44 vout_command, vout_max, vout_margin_ high, vout_margin_low, vout_ov_fault_limit, vout_ov_warn_limit, vout_uv_warn_limit, vout_uv_fault_limit, power_good_on and power_good_off .................................................. 45 mfr_vout_discharge_threshold .................... 45 mfr_dac .................................................................. 45 output current commands and limits .......................... 46 iout_cal_gain ....................................................... 46 iout_oc_fault_limit, iout_oc_warn_limit and iout_uc_fault_limit ............................................ 47 mfr_iout_cal_gain_tc ........................................ 47 external temperature commands and limits ................ 48 ot_fault_limit, ot_warn_limit, ut_warn_ limit and ut_fault_limit ..................................... 48 mfr_temp_1_gain and mfr_temp_1_offset ...... 48 mfr_t_self_heat, mfr_iout_cal_gain_tau_inv and mfr_iout_cal_gain_theta .......................... 49 sequencing timing limits and clock sharing ................ 51 ton_delay, ton_rise, ton_max_fault_limit and toff_delay ....................................................... 51 mfr_restart_delay ............................................. 51 watchdog timer and power good ................................. 52 mfr_pwrgd_en ..................................................... 52 clock sharing ............................................................ 52 mfr_powergood_assertion_delay ................ 53 watchdog operation .................................................. 53 mfr_watchdog_t_first and mfr_watchdog_t .................................................. 53 fault responses ............................................................. 54 clearing latched faults ............................................. 54 vout_ov_fault_response and vout_uv_fault_ response ................................................................ 55 iout_oc_fault_response and iout_uc_fault_ response ................................................................ 56 ot_fault_response, ut_fault_response, vin_ov_fault_response and vin_uv_fault_ response ................................................................ 57 ton_max_fault_response ................................. 58 mfr_retry_delay ................................................. 58 mfr_retry_count ................................................ 58 shared external faults ................................................... 59 mfr_faultb0_propagate and mfr_faultb1_ propagate .............................................................. 59
ltc2974 3 2974fa for more information www.linear.com/ltc2974 mfr_faultb0_response and mfr_faultb1_ response ................................................................ 60 fault warning and status ............................................... 61 clear_faults ......................................................... 61 status_byte ........................................................... 61 status_word ......................................................... 62 status_vout .......................................................... 62 status_iout ........................................................... 63 status_input ......................................................... 63 status_temperature ........................................... 63 status_cml ............................................................ 64 status_mfr_specific ........................................... 64 mfr_pads ................................................................ 65 mfr_common ......................................................... 65 telemetry ....................................................................... 66 read_vin ................................................................. 67 read_vout .............................................................. 67 read_iout ............................................................... 67 read_temperature_1 .......................................... 67 read_temperature_2 .......................................... 67 read_pout .............................................................. 67 mfr_read_iout ..................................................... 67 mfr_iout_sense_voltage ................................... 68 mfr_vin_peak ........................................................ 69 mfr_vout_peak ..................................................... 69 mfr_iout_peak ...................................................... 69 mfr_temperature_1_peak ................................. 69 mfr_vin_min .......................................................... 69 mfr_vout_min ....................................................... 69 mfr_iout_min ........................................................ 69 mfr_temperature_1_min ................................... 69 fault logging ................................................................. 70 fault log operation ................................................... 70 mfr_fault_log_store ........................................ 70 mfr_fault_log_restore .................................... 70 mfr_fault_log_clear ........................................ 71 mfr_fault_log_status ....................................... 71 mfr_fault_log ...................................................... 71 mfr_fault_log read example .............................. 74 identification/information .............................................. 78 capability ............................................................... 79 pmbus_revision ..................................................... 79 mfr_special_id ..................................................... 79 mfr_special_lot .................................................. 79 user scratchpad ............................................................. 79 user_data_00, user_data_01, user_data_02, user_data_03, user_data_04, mfr_ltc_ reserved_1 and mfr_ltc_reserved_2 ............. 79 applications information ...................................... 80 overview ........................................................................ 80 powering the ltc2974 ................................................... 80 setting command register values ................................. 80 sequence, servo, margin and restart operations ......... 80 command units on or off ......................................... 80 on sequencing .......................................................... 80 on state operation .................................................... 81 servo modes ............................................................. 81 dac modes ................................................................ 82 margining .................................................................. 82 off sequencing .......................................................... 82 v out off threshold voltage ....................................... 82 automatic restart via mfr_restart_delay command and control pin .................................... 82 fault management .......................................................... 82 output overvoltage, undervoltage, overcurrent, and undercurrent faults ................................................... 82 output overvoltage, undervoltage, and overcurrent warnings ................................................................... 83 configuring the auxfaultb output .......................... 83 multi-channel fault management .............................. 84 interconnect between multiple ltc2974s ..................... 84 application circuits ........................................................ 85 trimming and margining dc/dc converters with external feedback resistors ..................................... 85 four-step resistor selection procedure for dc/dc converters with external feedback resistors ........... 85 trimming and margining dc/dc converters with a trim pin .................................................................... 86 two-step resistor and dac full-scale voltage selection procedure for dc/dc converters with a trim pin .................................................................... 87 measuring current with a sense resistor ................. 87 measuring current with inductor dcr ...................... 87 single phase design example ................................... 88 measuring multiphase currents ................................ 88 multiphase design example ...................................... 89 anti-aliasing filter considerations ............................. 89 sensing negative voltages ........................................ 89 connecting the dc1613 usb to i 2 c/smbus/pmbus controller to the ltc2974 in system ......................... 90 accurate dcr temperature compensation .................... 91 ltpowerplay: an interactive gui for power managers ... 93 pcb assembly and layout suggestions ........................ 94 bypass capacitor placement ..................................... 94 exposed pad stencil design ...................................... 94 unused adc sense inputs ......................................... 94 pcb board layout ..................................................... 94 package description ........................................... 95 typical application ............................................. 96 related parts .................................................... 96 table of contents
ltc2974 4 2974fa for more information www.linear.com/ltc2974 pin configuration absolute maximum ratings supply voltages: v pwr to gnd ......................................... C0.3v to 15v v dd33 to gnd ....................................... C0.3v to 3.6v v dd25 to gnd ..................................... C0.3v to 2.75v digital input/output voltages: alertb, sda, scl, control0, control1, control2, control3 to gnd ........... C0.3v to 3.6v pwrgd, share_clk, wdi/resetb, wp, faultb0, faultb1 to gnd ................. C0.3v to 3.6 v asel0, asel1 to gnd .......................... C0.3v to 3.6v analog voltages: refp ................................................... C0.3v to 1.35v refm to gnd ........................................ C0.3v to 0.3v v in_sns to gnd ...................................... C0.3v to 15v v sensep[3:0] to gnd ................................. C0.3v to 6v v sensem[3:0] to gnd ................................ C0.3v to 6v i sensep[3:0] to gnd .................................. C0.3v to 6v i sensem[3:0] to gnd ................................. C0.3v to 6v v out_en[3:0] , auxfaultb to gnd .......... C0.3v to 15v v dac[3:0] to gnd ...................................... C0.3v to 6v t sense[3:0] to gnd ................................ C0.3v to 3.6v operating junction temperature range: ltc2974c ................................................ 0c to 70c ltc2974i .............................................. C40c to 85c storage temperature range .................. C65c to 125c maximum junction temperature ........................ 125c* *see operation section for detailed eeprom de- rating information for junction temperatures in excess of 85c. (note 1) order information top view 65 gnd up package 64-lead (9mm 9mm) plastic qfn v sensep0 1 v sensem0 2 v out_en0 3 v out_en1 4 v out_en2 5 v out_en3 6 auxfaultb 7 dnc 8 v in_sns 9 v pwr 10 v dd33 11 v dd33 12 v dd25 13 v dd25 14 t sense0 15 t sense1 16 48 i sensem3 47 i sensep3 46 i sensem2 45 i sensep2 44 i sensem1 43 i sensep1 42 i sensem0 41 i sensep0 40 refm 39 gnd 38 refp 37 gnd 36 asel1 35 asel0 34 t sense3 33 control1 64 v sensem1 63 v sensep1 62 v sensem2 61 v sensep2 60 nc 59 nc 58 v dac3 57 v dac2 56 nc 55 nc 54 v dac1 53 v dac0 52 nc 51 nc 50 v sensem3 49 v sensep3 pwrgd 17 share_clk 18 gnd 19 gnd 20 gnd 21 control2 22 control3 23 wdi/resetb 24 faultb0 25 faultb1 26 t sense2 27 wp 28 sda 29 scl 30 alertb 31 control0 32 t jmax = 125c, jctop = 7c/w, jcbottom = 1c/w exposed pad (pin 65) is gnd, must be soldered to pcb lead free finish tape and reel part marking* package description temperature range ltc2974cup#pbf ltc2974cup#trpbf ltc2974up 64-lead (9mm 9mm) plastic qfn 0c to 70c ltc2974iup#pbf ltc2974iup#trpbf ltc2974up 64-lead (9mm 9mm) plastic qfn C40c to 85c consult ltc marketing for parts specified with wider operating temperature ranges. *the temperature grade is identified by a label on the shipping container. consult ltc marketing for information on non-standard lead based finish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ltc2974 5 2974fa for more information www.linear.com/ltc2974 electrical characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t j = 25c. v pwr = v in_sns = 12v, v dd33 , v dd25 , refp and refm pins floating, unless otherwise indicated. c vdd33 = 100nf, c vdd25 = 100nf and c ref = 100nf. symbol parameter conditions min typ max units power supply characteristics v pwr v pwr supply input operating range v dd33 floating (note 2) l 4.5 15 v i pwr v pwr supply current 4.5v v pwr 15v, v dd33 floating (note 2) l 10 13 ma i vdd33 v dd33 supply current 3.13v v dd33 3.47v, v pwr = v dd33 l 10 13 ma v uvlo_vdd33 v dd33 undervoltage lockout v dd33 ramping up, v pwr = v dd33 l 2.25 2.55 2.8 v v dd33 undervoltage lockout hysteresis 120 mv v dd33 supply input operating range v pwr = v dd33 l 3.13 3.47 v regulator output voltage 4.5v v pwr 15v l 3.13 3.26 3.47 v regulator output short-circuit current v pwr = 4.5v, v dd33 = 0v l 75 90 140 ma v dd25 regulator output voltage 3.13v v dd33 3.47v l 2.35 2.5 2.6 v regulator output short-circuit current v pwr = v dd33 = 3.47v, v dd25 = 0v l 30 55 80 ma t init initialization time time from v in applied until the ton_delay timer starts 30 ms voltage reference characteristics v ref output voltage v ref = v refp C v refm , 0 < i refp < 100a l 1.220 1.232 1.244 v temperature coefficient 3 ppm/c hysteresis (note 3) 100 ppm adc characteristics v in_adc voltage sense input range differential voltage: v in_adc = (v sensepn C v sensemn ) l 0 6 v single-ended voltage: v sensemn l C0.1 0.1 v current sense input range single-ended voltage: i sensepn , i sensemn l C0.1 6 v differential current sense voltage: v in_adc = (i sensepn C i sensemn ) l C170 170 mv n_adc voltage sense resolution 0v v in_adc 6v, read_vout 122 v/lsb current sense resolution 0mv |v in_adc | < 16mv (note 4) 16mv |v in_adc | < 32mv 32mv |v in_adc | < 63.9mv 63.9mv |v in_adc | < 127.9mv 127.9mv |v in_adc | iout_cal_gain = 1000m 15.625 31.25 62.5 125 250 a/lsb a/lsb a/lsb a/lsb a/lsb tue_adc_ volt_sns total unadjusted error voltage sense inputs v in_adc 1v l 0.25 % voltage sense inputs 0 v in_adc 1v l 2.5 mv tue_adc_ curr_sns total unadjusted error current sense inputs 20mv v in_adc 170mv l 0.3 % current sense inputs v in_adc 20mv l 60 v v os_adc offset error i sensepn and i sensemn inputs, v os ? iout_ cal_gain, iout_cal_gain = 1 l 35 v t conv_adc conversion time v sensepn , v sensemn , v in_sns inputs (note 5) 6.15 ms i sensepn and i sensemn inputs (note 5) 24.6 ms internal temperature (read_temperature_2) (note 5) 24.6 ms
ltc2974 6 2974fa for more information www.linear.com/ltc2974 the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t j = 25c. v pwr = v in_sns = 12v, v dd33 , v dd25 , refp and refm pins floating, unless otherwise indicated. c vdd33 = 100nf, c vdd25 = 100nf and c ref = 100nf. symbol parameter conditions min typ max units t update_adc maximum update time (note 5) 160 ms c in_adc input sampling capacitance 1 pf f in_adc input sampling frequency 62.5 khz i in_adc input leakage current i sensepn , i sensemn ,v sensepn , and v sensemn inputs, v in_adc = 0v, 0v v commonmode 6v l 0.5 a differential input current v sensepn , and v sensemn inputs, v in_adc = 6v l 10 15 a i sensepn , and i sensemn inputs, v in_adc = 0.17v l 0.3 0.5 a dac output characteristics n_v dac resolution 10 bits v fs_vdac full-scale output voltage (programmable) dac code = 0x3ff dac polarity = 1 buffer gain setting_0 buffer gain setting_1 l l 1.3 2.5 1.38 2.65 1.44 2.77 v v inl_v dac integral nonlinearity (note 6) l 2 lsb dnl_v dac differential nonlinearity (note 6) l 2.4 lsb v os_vdac offset voltage (note 6) l 12 mv v dac load regulation v dacn = 2.65v, i vdacn sourcing = 2ma 100 ppm/ma v dacn = 0.1v, i vdacn sinking = 2ma 100 ppm/ma psrr dc: 3.13v v dd33 3.47v, v pwr = v dd33 60 db leakage current v dacn hi-z, 0v v dacn 6v l 100 na short-circuit current low v dacn shorted to gnd l C12 C4 ma short-circuit current high v dacn shorted to v dd33 l 4 12 ma c out output capacitance v dacn hi-z 10 pf t s_vdac dac output update rate fast servo mode 250 s voltage supervisor characteristics v in_vs input voltage range (programmable) v in_vs = (v sensepn C v sensemn ) low resolution mode high resolution mode l l 0 0 6 3.8 v v single-ended voltage: v sensemn l C0.1 0.1 v n_vs voltage sensing resolution 0v to 3.8v range: high resolution mode 4 mv/lsb 0v to 6v range: low resolution mode 8 mv/lsb tue_vs total unadjusted error 2v v in_vs 6v, low resolution mode l 1.25 % 1.5v < v in_vs 3.8v, high resolution mode l 1.0 % 0.8v v in_vs 1.5v, high resolution mode l 1.5 % t s_vs update rate 12.21 s current supervisor characteristics v in_cs current sense input range single-ended voltage: i sensepn , i sensemn l C0.1 6 v differential voltage: v in_cs = (i sensep n C i sensem n ) l C170 170 mv n_cs current sense resolution iout_oc_fault_limit ? iout_cal_gain iout_uc_fault_limit ? iout_cal_gain 400 v/lsb tue_cs total unadjusted error 50mv v in_cs 170mv l 3 % v in_cs < 50mv l 1.5 mv electrical characteristics
ltc2974 7 2974fa for more information www.linear.com/ltc2974 the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t j = 25c. v pwr = v in_sns = 12v, v dd33 , v dd25 , refp and refm pins floating, unless otherwise indicated. c vdd33 = 100nf, c vdd25 = 100nf and c ref = 100nf. symbol parameter conditions min typ max units v os_cs offset error |v in_cs | = 0.8mv l 600 v i os_cs differential input offset current oc = positive full-scale, uc = 0a, vin_cs = 0v 117 na oc = uc = positive full-scale, vin_cs = 0v 244 na oc = 0a, uc < 0a, vin_cs = 0v 0 na t s_cs update rate 12.21 s v in_sns input characteristics v in_sns v in_sns input voltage range l 0 15 v r vin_sns v in_sns input resistance l 70 90 110 k tue vin_sns vin_on, vin_off threshold total unadjusted error 3v v vin_sns 8v l 2.0 % v vin_sns > 8v l 1.0 % read_vin total unadjusted error 3v v vin_sns 8v l 1.5 % v vin_sns > 8v l 1.0 % dac soft-connect comparator characteristics v os_cmp offset voltage l 3 18 mv external temperature sensor characteristics (read_temperature_1) t conv_tsense conversion time for one channel, (total latency for all channels is 4 ? 66ms) 66 ms i tsense_hi t sense high level current l C90 C64 C40 a i tsense_low t sense low level current l C5.5 C4 C2.5 a tue_ts total unadjusted error ideal diode assumed l 3 c n_ts maximum ideality factor read_temperature_1 = 175c mfr_temp1_gain = 1/n_ts 1.10 na internal temperature sensor characteristics (read_temperature_2) tue_ts2 total unadjusted error 1 c v out enable output (v out_en[3:0] ) characteristics v vout_enn output high voltage i vout_enn = C5a, v dd33 = 3.13v l 12 13 14.7 v i vout_enn output sourcing current v vout_enn pull-up enabled, v vout_enn = 1v l C5 C7 C9 a output sinking current strong pull-down enabled, v vout_enn = 0.4v l 3 5 8 ma weak pull-down enabled, v vout_enn = 0.4v l 33 50 65 a output leakage current internal pull-up disabled, 0v v vout_enn 15v l 1 a general purpose output (auxfaultb) characteristics v auxfaultb output high voltage i auxfaultb = C5a, v dd33 = 3.13v l 12 13 14.7 v i auxfaultb output sourcing current auxfaultb pull-up enabled, v auxfaultb = 1v l C5 C7 C9 a output sinking current strong pull-down enabled, v auxfaultb = 0.4v l 3 5 8 ma output leakage current internal pull-up disabled, 0v v auxfaultb 15v l 1 a eeprom characteristics endurance (note 7) 0c < t j < 85c during eeprom write operations l 10,000 cycles electrical characteristics
ltc2974 8 2974fa for more information www.linear.com/ltc2974 symbol parameter conditions min typ max units retention (note 7) t j < 85c l 10 years t mass_write mass write operation time (note 8) store_user_all, 0c < t j < 85c during eeprom write operations l 440 4100 ms digital inputs scl, sda, control0, control1, control2, control3, wdi/resetb, faultb0, faultb1, wp v ih high level input voltage faultb0, faultb1, sda, scl, wdi/resetb, wp l 2.1 v controln l 1.85 v v il low level input voltage faultb0, faultb1, sda, scl, wdi/resetb, wp l 1.5 v controln l 1.6 v v hyst input hysteresis 20 mv i leak input leakage current 0v v pin 3.6v l 2 a t sp pulse width of spike suppressed faultb0, faultb1, control n 10 s sda, scl 98 ns t fault_min minimum low pulse width for externally generated faults 180 ms t resetb pulse width to assert reset v wdi/resetb 1.5v l 300 s t wdi pulse width to reset watchdog timer v wdi/resetb 1.5v l 0.3 200 s f wdi watchdog timer interrupt input frequency l 1 mhz c in input capacitance 10 pf digital input share_clk v ih high level input voltage l 1.6 v v il low level input voltage l 0.8 v f share_clk_in input frequency operating range l 90 110 khz t low assertion low time v share_clk < 0.8v l 0.825 1.11 s t rise rise time v share_clk < 0.8v to v share_clk > 1.6v l 450 ns i leak input leakage current 0v v share_clk v dd33 + 0.3v l 1 a c in input capacitance 10 pf digital outputs sda, alertb, share_clk, faultb0, faultb1, pwrgd v ol digital output low voltage i sink = 3ma l 0.4 v f share_clk_out output frequency operating range 5.49k pull-up to v dd33 l 90 100 110 khz digital inputs asel0,asel1 v ih input high threshold voltage l v dd33 C 0.5 v v il input low threshold voltage l 0.5 v i ih,il high, low input current asel[1:0] = 0, v dd33 l 95 a i ih,z hi-z input current l 24 a c in input capacitance 10 pf serial bus timing characteristics f scl serial clock frequency (note 9) l 10 400 khz t low serial clock low period (note 9) l 1.3 s t high serial clock high period (note 9) l 0.6 s the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t j = 25c. v pwr = v in_sns = 12v, v dd33 , v dd25 , refp and refm pins floating, unless otherwise indicated. c vdd33 = 100nf, c vdd25 = 100nf and c ref = 100nf. electrical characteristics
ltc2974 9 2974fa for more information www.linear.com/ltc2974 the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t j = 25c. v pwr = v in_sns = 12v, v dd33 , v dd25 , refp and refm pins floating, unless otherwise indicated. c vdd33 = 100nf, c vdd25 = 100nf and c ref = 100nf. note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: all currents into device pins are positive. all currents out of device pins are negative. all voltages are referenced to ground unless otherwise specified. if power is supplied to the chip via the v dd33 pin only, connect v pwr and v dd33 pins together. note 3: hysteresis in the output voltage is created by package stress that differs depending on whether ic was previously at a higher or lower temperature. output voltage is always measured at 25c, but the ic is cycled to 85c or C40c before successive measurements. hysteresis is roughly proportional to the square of the temperature change. note 4: the current sense resolution is determined by the l11 format and the mv units of the returned value. for example, a full-scale value of 170mv returns a l11 value of 0xf2a8 = 680 ? 2 C2 = 170. this is the lowest range that can represent this value without overflowing the l11 mantissa and the resolution for 1lsb in this range is 2 C2 ma = 250a. each successively lower range improves resolution by cutting the lsb size in half. note 5: the nominal time between successive adc conversions (latency of the adc) for any given channel is t update_adc . note 6: nonlinearity is defined from the first code that is greater than or equal to the maximum offset specification to full-scale code, 1023. note 7: eeprom endurance and retention are guaranteed by design, characterization and correlation with statistical process controls. the minimum retention specification applies for devices whose eeprom has been cycled less than the minimum endurance specification. note 8: the ltc2974 will not acknowledge any pmbus commands, except for mfr_common, when a store_user_all command is being executed. see also operation section. note 9: maximum capacitive load, c b , for scl and sda is 400pf. data and clock risetime (t r ) and falltime (t f ) are: (20 + 0.1? c b ) (ns) < t r < 300ns and (20 + 0.1 ? c b ) (ns) < t f < 300ns. c b = capacitance of one bus line in pf. scl and sda external pull-up voltage, v io , is 3.13v < v io < 3.6v. electrical characteristics pmbus timing diagram sda scl t hd(sta) t hd(dat) t su(sta) t su(sto) t su(dat) t low t hd(sta) t sp t buf start condition stop condition repeated start condition start condition t r t f t r t f t high 2974 td symbol parameter conditions min typ max units t buf bus free time between stop and start (note 10) l 1.3 s t hd,sta start condition hold time (note 9) l 600 ns t su,sta start condition setup time (note 9) l 600 ns t su,sto stop condition setup time (note 9) l 600 ns t hd,dat data hold time (ltc2974 receiving data) (note 9) l 0 ns data hold time (ltc2974 transmitting data) (note 9) l 300 900 ns t su,dat data setup time (note 9) l 100 ns t sp pulse width of spike suppressed (note 9) 98 ns t timeout_bus time allowed to complete any pmbus command after which time sda will be released and command terminated longer timeout = 0 longer timeout = 1 l l 25 200 35 280 ms ms additional digital timing characteristics t off_min minimum off time for any channel 100 ms
ltc2974 10 2974fa for more information www.linear.com/ltc2974 typical performance characteristics adc read_iout input referred noise vs temperature input sampling current vs differential input voltage: voltage sense inputs input sampling current vs differential input voltage: current sense inputs adc read_vout-inl adc read_vout-dnl adc read_iout error vs read_iout reference voltage vs temperature adc read_vout total unadjusted error vs temperature adc read_iout input referred offset voltage vs temperature temperature (c) ?50 reference output voltage (v) 50 75 1.2322 1.2320 1.2318 1.2316 1.2314 1.2312 1.2310 1.2308 1.2306 1.2304 2974 g01 ?25 0 25 100 three typical parts temperature (c) ?50 error (%) 50 75 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 ?0.03 ?0.02 ?0.01 2974 g02 ?25 0 25 100 three typical parts temperature (c) ?50 offset (v) 50 75 5 4 3 2 1 0 ?1 ?2 ?5 ?4 ?3 2974 g03 ?25 0 25 100 three typical parts read_vout (v) 0 error (lsbs) 6 5 4 3 2 0 1 ?1 ?2 ?3 ?4 ?5 2974 g04 1 2 3 4 5 122v/lsb read_vout (v) 0 error (lsbs) 6 5 4 3 2 0 1 ?1 ?2 ?3 ?4 ?5 2974 g05 1 2 3 4 5 122v/lsb 0.001 0.01 10 100 10.1 read_iout (a) read_iout error (ma) 75 50 25 0 ?25 ?50 ?75 2974 g06 iout_cal_gain = 2.1875m differential input voltage (v) 0 differential input current (a) 4 5 7 6 5 4 3 2 1 0 2974 g08 1 2 3 6 temperature (c) ?50 noise (v rms ) 50 75 4.50 4.25 4.00 3.75 3.50 3.25 3.00 2.75 2.50 2974 g07 ?25 0 25 100 differential input voltage (mv) 0 differential input current (na) 100 150125 400 350 300 250 200 150 50 100 0 2974 g09 25 50 75 175 v cm = 2.5v
ltc2974 11 2974fa for more information www.linear.com/ltc2974 voltage supervisor total unadjusted error vs temperature current supervisor total unadjusted error vs temperature dac full-scale voltage vs temperature, gain = 0 typical performance characteristics dac-inl dac-dnl v dd33 regulator output voltage vs temperature dac full-scale voltage vs temperature, gain = 1 dac offset voltage vs temperature, gain = 0 dac offset voltage vs temperature, gain = 1 temperature (c) ?50 supervisor error (%) 50 75 0.25 0.20 0.15 0.10 0.05 0 ?0.05 ?0.10 ?0.15 ?0.20 2974 g10 ?25 0 25 100 three typical parts high res mode v in = 1.5v temperature (c) ?50 dac output voltage (v) 50 75 1.405 1.400 1.395 1.390 1.385 1.380 1.375 1.370 1.365 1.360 2974 g12 ?25 0 25 100 three typical parts gain setting = 0 temperature (c) ?50 output voltage (v) 50 75 3.285 3.280 3.275 3.270 3.265 3.260 3.255 3.250 3.245 3.240 2974 g18 ?25 0 25 100 three typical parts temperature (c) ?50 dac output voltage (v) 50 75 2.70 2.69 2.68 2.67 2.66 2.65 2.64 2.63 2.62 2974 g13 ?25 0 25 100 three typical parts gain setting = 1 dac code 0 error (lsbs) 1.00 0.75 0.50 0.25 0 ?0.25 ?0.50 ?0.75 ?1.00 768 2974 g16 256 512 1024 dac code 0 error (lsbs) 1.00 0.75 0.50 0.25 0 ?0.25 ?0.50 ?0.75 ?1.00 768 2974 g17 256 512 1024 temperature (c) ?50 dac output voltage (v) 50 75 0.0025 0.0020 0.0015 0.0010 0.0005 0 2974 g14 ?25 0 25 100 three typical parts gain setting = 0 temperature (c) ?50 dac output voltage (v) 50 75 0.0040 0.0030 0.0025 0.0035 0.0020 0.0015 0.0010 0.0005 0 2974 g15 ?25 0 25 100 three typical parts gain setting = 1 temperature (c) ?50 supervisor error (%) 50 75 2974 g11 ?25 0 25 100 50mv 20mv 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0
ltc2974 12 2974fa for more information www.linear.com/ltc2974 typical performance characteristics pwrgd and faultb n v ol vs current sinking external temperature read_ temperature_1 error vs temperature alertb v ol vs current sinking read_temperature_2 error vs temperature v dd33 regulator load regulation v vout_enn and v auxfaultb output v oh vs current sourcing v vout_enn and v auxfaultb output v ol vs current sinking load current sourcing (ma) 0 output voltage delta (ppm) 30 40 0 ?1000 ?2000 ?3000 ?4000 2974 g19 10 20 50 current sourcing (a) 0 output high voltage (v) 4 5 14.0 13.5 13.0 12.5 12.0 11.5 11.0 10.5 10.0 9.5 9.0 2974 g20 1 2 3 876 25c 85c ?40c current sinking (ma) 0 1.4 1.2 1.0 0.8 85c ?40c 0.6 0.4 0.2 0 6 10 2974 g21 2 4 8 12 v ol (v) 25c current sinking (ma) 0 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 15 2974 g22 5 10 20 v ol (v) 85c 25c ?40c temperature (c) ?50 error (%) 50 75 1.00 0.50 0.25 0.75 0 ?0.25 ?0.50 ?0.75 ?1.00 2974 g24 ?25 0 25 100 three typical parts mmbt3906 diode connected bjts mfr_temp_1_gain_adj = 0.987 mfr_ext_temp_1_adc_off = ?2c temperature (c) ?50 error (%) 50 75 1.00 0.50 0.25 0.75 0 ?0.25 ?0.50 ?0.75 ?1.00 2974 g25 ?25 0 25 100 three typical parts v dd33 = v pwr = 3.3v current sinking (ma) 0 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 2974 g23 5 10 15 v ol (v) 85c 25c ?40c
ltc2974 13 2974fa for more information www.linear.com/ltc2974 pin functions pin name pin number pin type description v sensep0 1* in dc/dc converter differential (+) output voltage-0 sensing pin v sensem0 2* in dc/dc converter differential (C) output voltage-0 sensing pin v out_en0 3 out dc/dc converter enable-0 pin. output high voltage optionally pulled-up to 12v by 5a v out_en1 4 out dc/dc converter enable-1 pin. output high voltage optionally pulled-up to 12v by 5a v out_en2 5 out dc/dc converter enable-2 pin. output high voltage optionally pulled-up to 12v by 5a v out_en3 6 out dc/dc converter enable-3 pin. output high voltage optionally pulled-up to 12v by 5a auxfaultb 7 out auxillary fault output pin. output high voltage optionally pulled-up to 12v by 5a. can be configured to pull low when ov/uv/oc/uc detected dnc 8 do not connect do not connect to this pin v in_sns 9 in v in sense input. this voltage is compared against the v in on and off voltage thresholds in order to determine when to enable and disable, respectively, the downstream dc/dc converters v pwr 10 in v pwr serves as the unregulated power supply input to the chip (4.5 to 15v). if a 4.5v to 15v supply voltage is unavailable, short v pwr to v dd33 and power the chip directly from a 3.3v supply. bypass to gnd with 0.1f capacitor. v dd33 11 in/out if shorted to v pwr , it serves as 3.13 to 3.47v supply input pin. otherwise it is a 3.3v internally regulated voltage output (use 0.1f decoupling capacitor to gnd) v dd33 12 in input for internal 2.5v sub-regulator. short this pin to pin 11 v dd25 13 in/out 2.5v internally regulated voltage output. bypass to gnd with a 0.1f capacitor v dd25 14 in 2.5v supply voltage input. short this pin to pin 13 t sense0 15* in/out external temperature current output and voltage input for channel 0. maximum allowed capacitance is 1f t sense1 16* in/out external temperature current output and voltage input for channel 1. maximum allowed capacitance is 1f pwrgd 17 out power-good open drain output. indicates when selected outputs are power good. can be used as system power-on reset share_clk 18 in/out bidirectional clock sharing pin. connect a 5.49k? pull-up resistor to v dd33 gnd 19 ground chip ground. must be soldered to pcb gnd 20 ground chip ground. must be soldered to pcb gnd 21 ground chip ground. must be soldered to pcb control2 22 in control pin 2 input control3 23 in control pin 3 input wdi/resetb 24 in watchdog timer interrupt and chip reset input. connect a 10k? pull-up resistor to v dd33 . rising edge resets watchdog counter. holding this pin low for more than t resetb resets the chip faultb0 25 in/out open-drain output and digital input. active low bidirectional fault indicator-0. connect a 10k? pull-up resistor to v dd33 faultb1 26 in/out open-drain output and digital input. active low bidirectional fault indicator-1. connect a 10k? pull-up resistor to v dd33 t sense2 27* in/out external temperature current output and voltage input for channel 2. maximum allowed capacitance is 1f wp 28 in digital input. write-protect input pin, active high sda 29 in/out pmbus bidirectional serial data pin scl 30 in pmbus serial clock input pin (400khz maximum) alertb 31 out open-drain output. generates an interrupt request in a fault/warning situation control0 32 in control pin 0 input control1 33 in control pin 1 input
ltc2974 14 2974fa for more information www.linear.com/ltc2974 pin name pin number pin type description t sense3 34* in/out external temperature current output and voltage input for channel 3. maximum allowed capacitance is 1f asel0 35 in ternary address select pin 0 input. connect to v dd33 , gnd or float to encode 1 of 3 logic states asel1 36 in ternary address select pin 1 input. connect to v dd33 , gnd or float to encode 1 of 3 logic states gnd 37 ground chip ground. must be soldered to pcb refp 38 out reference voltage output. needs 0.1f decoupling capacitor to refm gnd 39 ground chip ground. must be soldered to pcb refm 40 out reference return pin. needs 0.1f decoupling capacitor to refp i sensep0 41* in dc/dc converter differential (+) output current-0 sensing pin i sensem0 42* in dc/dc converter differential (C) output current-0 sensing pin i sensep1 43* in dc/dc converter differential (+) output current-1 sensing pin i sensem1 44* in dc/dc converter differential (C) output current-1 sensing pin i sensep2 45* in dc/dc converter differential (+) output current-2 sensing pin i sensem2 46* in dc/dc converter differential (C) output current-2 sensing pin i sensep3 47* in dc/dc converter differential (+) output current-3 sensing pin i sensem3 48* in dc/dc converter differential (C) output current-3 sensing pin v sensep3 49* in dc/dc converter differential (+) output voltage-3 sensing pin v sensem3 50* in dc/dc converter differential (C) output voltage-3 sensing pin nc 51 no connect no connect nc 52 no connect no connect v dac0 53 out dac0 output v dac1 54 out dac1 output nc 55 no connect no connect nc 56 no connect no connect v dac2 57 out dac2 output v dac3 58 out dac3 output nc 59 no connect no connect nc 60 no connect no connect v sensep2 61* in dc/dc converter differential (+) output voltage-2 sensing pin v sensem2 62* in dc/dc converter differential (C) output voltage-2 sensing pin v sensep1 63* in dc/dc converter differential (+) output voltage-1 sensing pin v sensem1 64* in dc/dc converter differential (C) output voltage-1 sensing pin gnd 65 ground exposed pad. must be soldered to pcb *any unused v sensep n /i sensep n , v sensem n /i sensem n or t sense n pins should be tied to gnd. pin functions
ltc2974 15 2974fa for more information www.linear.com/ltc2974 block diagram 10 3.3v regulator internal temp sensor reference 1.232v (typ) masking clock generation oscillator uvlo porb v dd external temperature sensor eeprom ram adc_results monitor limits servo targets pmbus interface (400khz i 2 c compatible) controller pmbus algorithm fault processor watchdog sequencer v in v dd33 v sensep0 v sensem0 v out v pwr 12 2.5v regulator v in v out v dd33(in) 1 2 v dac0 v dac1 v dac2 v dac3 nc nc nc nc nc nc page 0 page 1 page 2 page 3 3 v out_en0 4 v out_en1 5 v out_en2 6 v out_en3 15 t sense0 16 t sense1 27 t sense2 34 t sense3 2974 bd 7 auxfaultb 13 v dd25(out) 14 v dd25(in) v dd25 19 gnd 20 gnd 21 gnd 37 gnd 39 gnd 65 gnd 31 alertb 30 scl 29 sda 35 asel0 36 asel1 28 wp 23 control3 17 pwrgd share_clk 18 24 wdi/resetb 25 faultb0 26 faultb1 32 control0 33 22 control2 control1 11 v dd33(out) 9 v in_sns 8 dnc refp refm 3r r 20 i sensep0 i sensem0 v sensep1 v sensem1 i sensep1 i sensem1 v sensep2 v sensem2 i sensep2 i sensem2 v sensep3 v sensem3 i sensep3 i sensem3 16-bit ? adc adc clocks v dd33 + ? + ? 38 40 10-bit vdac + ? ? + vcmp vbuf 10-bit dac 41 42 63 64 43 44 61 62 45 46 49 50 53 54 57 58 51 52 55 56 59 60 v sensem0 v sensep0 i sensep0 i sensem0 v sensem1 v sensep1 i sensep1 i sensem1 v sensem2 v sensep2 i sensep2 i sensem2 v sensem3 v sensep3 i sensep3 48 i sensem3 47 mux + ? 10-bit vdac + ? ? + icmp
ltc2974 16 2974fa for more information www.linear.com/ltc2974 operation ltc2974 operation overview the ltc2974 is a pmbus programmable power supply controller, monitor, sequencer and voltage and current supervisor that can perform the following operations: ? accept pmbus compatible programming commands. ? provide dc/dc converter input voltage, output voltage, output current, output temperature, and internal junction temperature readback through the pmbus interface. ? control the output of dc/dc converters that set the output voltage with a trim pin or dc/dc converters that set the output voltage using an external resistor feedback network. ? sequence the startup of dc/dc converters via pmbus programming and the control input pins. the ltc 2974 supports time-based sequencing and tracking sequencing. cascade sequence on with time based sequence off is also supported. ? trim the dc/dc converter output voltage (typically in 0.02% steps), in closed-loop servo operating mode, autonomously or through pmbus programming. ? margin the dc/dc converter output voltage to pmbus programmed limits. ? trim or margin the dc/dc converter output voltage with direct access to the margin dac. ? supervise the dc/dc converter input voltage, output voltage, load current and the inductor temperatures for overvalue/undervalue conditions with respect to pmbus programmed limits and generate appropriate faults and warnings. ? accurately handle inductor self-heating transients using a proprietary algorithm. these self-heating effects are combined with external temperature sensor readings to improve accuracy of current supervisors and adc current measurement. ? respond to a fault condition by continuing operation indefinitely, latching-off after a programmable deglitch period, latching-off immediately or sequencing off after toff_delay. use retry mode to automatically recover from a latched-off condition. with retry enabled, mfr_retry_count programs the number of retries (0 to 6 or infinite) for all pages. ? optionally stop trimming the dc/dc converter output voltage after it reaches the initial margin or nominal target. optionally allow servo to resume if target drifts outside of v out warning limits. ? store command register contents with crc to eeprom through pmbus programming. ? restore eeprom contents through pmbus program - ming or when vdd33 is applied on power-up. ? report the dc/dc converter output voltage status through the power good output. ? generate interrupt requests by asserting the alertb pin in response to supported pmbus faults and warnings. ? coordinate system wide fault responses for all dc/dc converters connected to the ltc2974 faultb0 and faultb1 pins. ? synchronize sequencing delays or shutdown for multiple devices using the share_clk pin. ? software and hardware write protect the command registers. ? disable the input voltage to the supervised dc/dc converters in response to output ov, uv, oc and uc faults. ? log telemetry and status data to eeprom in response to a faulted-off condition. ? supervise an external microcontrollers activity for a stalled condition with a programmable watchdog timer and reset it if necessary. ? prevent a dc/dc converter from re-entering the on state after a power cycle until a programmable interval (mfr_restart_delay) has elapsed and its output has decayed below a programmable threshold voltage (mfr_vout_discharge_threshold). ? record minimum and maximum observed values of input voltage, output voltages, output currents and output temperatures. ? access user eeprom data directly, without alter - ing ram space (mfr_ee_unlock, mfr_ee_erase, and mfr_ee_data). facilitates in-house bulk programming.
ltc2974 17 2974fa for more information www.linear.com/ltc2974 operation figure 1: auxfaultb mux auxfaultb 2974 f01 fast pull-down ov/uv/oc/uc (maskable) off_then_on or fault_retry for any channel pmbus command fault_seen weak 12v pull-up hi-z reset set q eeprom the ltc2974 contains internal eeprom (non-volatile memory) to store configuration settings and fault log information. eeprom endurance, retention and mass write operation time are specified over the operating tem - perature range. see electrical characteristics and absolute maximum ratings sections. non destructive operation above t j = 85c is possible although the electrical characteristics are not guaranteed and the eeprom will be degraded. operating the eeprom above 85c may result in a deg - radation of retention characteristics. the fault logging function, which is useful in debugging system problems that may occur at high temperatures, only writes to fault log eeprom locations. if occasional writes to these reg - isters occur above 85c, a slight degradation in the data retention characteristics of the fault log may occur. it is recommended that the eeprom not be written using store_user_all or bulk programming when t j > 85c. the degradation in eeprom retention for temperatures >85c can be approximated by calculating the dimension - less acceleration factor using the following equation. af = e ea k ? ? ? ? ? ? ? 1 t use + 273 ? 1 t stress + 273 ? ? ? ? ? ? ? ? ? ? ? ? ? ? where: af = acceleration factor ea = activation energy = 1.4ev l?t C5 ev/k t use = 85c specified junction temperature t stress = actual junction temperature c example: calculate the effect on retention when operating at a junction temperature of 95c for 10 hours. t stress = 95c t use = 85c af = 3.4 equivalent operating time at 85c = 34 hours. so the overall rentention of the eeprom was degraded by 34 hours as a result of operation at a junction temperature of 95c for 10 hours. note that the effect of this overstress is negligible when compared to the overall eeprom rentention rating of 87,600 hours at a maximum junction temperature of 85c. auxfaultb the auxfaultb pin can be commanded to one of two output levels at any time via the pmbus. if desired, the auxfaultb pin can also be configured to indicate when some fault conditions have been detected, using a third output level. see figure 1 for a conceptual view of this multiplexing. the mfr_config2_ltc2974 and mfr_config3_ ltc2974 commands can be used on a per channel basis to select which, if any, fault conditions will cause the auxfaultb pin to be driven to its third output level (fast pull-down to gnd). the only fault types which can be propagated to the auxfaultb pin are over/under voltage faults and over/under current faults. mfr_config_all_auxfaultb_wpu selects whether the auxfaultb pin is in the hi-z state, or weakly pulled-up to approximately 12v, using a 5a current. as shown in figure 1, the pulldown to gnd overrides if any enabled faults are detected.
ltc2974 18 2974fa for more information www.linear.com/ltc2974 operation resetb holding the wdi/resetb pin low for more than t resetb will cause the ltc2974 to enter the power-on reset state. while in the power-on reset state, the device will not communicate on the i 2 c bus. following the subsequent rising-edge of the wdi/resetb pin, the ltc2974 will execute its power-on sequence per the user configuration stored in eeprom. connect wdi/resetb to vdd33 with a 10k resistor. wdi/resetb includes an internal 256s deglitch filter so additional filter capacitance on this pin is not recommended. pmbus serial digital interface the ltc2974 communicates with a host (master) using the standard pmbus serial bus interface. the pmbus timing diagram shows the timing relationship of the signals on the bus. the two bus lines, sda and scl, must be high when the bus is not in use. external pull-up resistors or current sources are required on these lines. the ltc2974 is a slave device. the master can communicate with the ltc2974 using the following formats: ? master transmitter, slave receiver ? master receiver, slave transmitter the following smbus commands are supported: ? write byte, write word, send byte ? read byte, read word, block read ? alert response address figures 1 to 12 illustrate the aforementioned smbus proto - cols. all transactions support pec (parity error check) and gcp (group command protocol). the block read supports 255 bytes of returned data. for this reason, the smbus timeout may be extended using the mfr_config_all_lon - ger_pmbus_timeout setting. pmbus pmbus is an industry standard that defines a means of communication with power conversion devices. it is comprised of an industry standard smbus serial interface and the pmbus command language. the pmbus two wire interface is an incremental extension of the smbus. smbus is built upon i 2 c with some minor differences in timing, dc parameters and protocol. the smbus protocols are more robust than simple i 2 c byte commands because they provide timeouts to prevent bus hangs and optional packet error checking (pec) to ensure data integrity. in general, a master device that can be configured for i 2 c communication can be used for pmbus communication with little or no change to hardware or firmware. for a description of the minor extensions and exceptions pmbus makes to smbus, refer to pmbus specification part 1 revision 1.1: section 5: transport. this can be found at: www.pmbus.org for a description of the differences between smbus and i 2 c, refer to system management bus (smbus) specification version 2.0: appendix b C differences between smbus and i 2 c. this can be found at: www.smbus.org when using an i 2 c controller to communicate with a pmbus part it is important that the controller be able to write a byte of data without generating a stop. this will allow the controller to properly form the repeated start of a pmbus read command by concatenating a start command byte write with an i 2 c read. device address the i 2 c/smbus address of the ltc2974 equals the base address + n where n is a number from 0 to 8. n can be configured by setting the asel0 and asel1 pins to v dd33 , gnd or float. see table 1. using one base address and the nine values of n, nine ltc2974s can be connected together to control thirty six outputs. the base address is stored in the mfr_i2c_base_address register. the base address can be written to any value, but generally should not be changed unless the desired range of addresses overlap existing addresses. watch that the address range does not overlap with other i 2 c/smbus device or global addresses, including i 2 c/smbus multiplexers and bus buffers. this will bring you great happiness.
ltc2974 19 2974fa for more information www.linear.com/ltc2974 operation the ltc2974 always responds to its global address and the smbus alert response address regardless of the state of its asel pins and the mfr_i2c_base_address register. processing commands the ltc2974 uses a dedicated processing block to ensure quick response to all of its commands. there are a few eeprom related commands command typical delay* comment store_user_all t mass_write see electrical characterization table. the ltc2974 will not accept any commands while it is transferring register contents to the eeprom. the command byte will be nacked. mfr_common may always be read. restore_user_all 30ms the ltc2974 will not accept any commands while it is transferring eeprom data to command registers. the command byte will be nacked. mfr_common may always be read. mfr_fault_log_clear 175ms the ltc2974 will not accept any commands while it is initializing the fault log eeprom space. the command byte will be nacked. mfr_common may always be read. mfr_fault_log_store 20ms the ltc2974 will not accept any commands while it is transferring fault log ram buffer to eeprom space. the command byte will be nacked. mfr_common may always be read. internal fault log 20ms an internal fault log event is a one time event that uploads the contents of the fault log to eeprom in response to a fault. internal fault logging may be disabled. commands received during this eeprom write are nacked. mfr_common may always be read. mfr_fault_log_restore 2ms the ltc2974 will not accept any commands while it is transferring eeprom data to the fault log ram buffer. the command byte will be nacked. mfr_common may always be read. *the typical delay is measured from the commands stop to the next commands start. exceptions where the part will nack a subsequent com - mand because it is still processing the previous command. these are summarized in the following tables. mfr_com - mon is a special command that may always be read even when the part is busy. this provides an alternate method for a host to determine if the ltc2974 is busy. other commands command delay* comment mfr_config <50s the ltc2974 will not accept any commands while it is completing this command. the command byte will be nacked. mfr_common may always be read. iout_cal_gain <500s the ltc2974 will not accept any commands while it is completing this command. the command byte will be nacked. mfr_common may always be read. *the typical delay is measured from the commands stop to the next commands start. other pmbus timing notes command comment clear_faults the ltc2974 will accept commands while it is completing this command but the affected status flags will not be cleared for up to 500s.
ltc2974 20 2974fa for more information www.linear.com/ltc2974 table 1. ltc2974 address look-up table with mfr_i2c_base_address set to 7bit 0x5c description hex device address binary device address address pins 7-bit 8-bit 6 5 4 3 2 1 0 r/w asel1 asel0 alert response 0c 19 0 0 0 1 1 0 0 1 x x global 5b b6 1 0 1 1 0 1 1 0 x x n = 0 5c* b8 1 0 1 1 1 0 0 0 l l n = 1 5d ba 1 0 1 1 1 0 1 0 l nc n = 2 5e bc 1 0 1 1 1 1 0 0 l h n = 3 5f be 1 0 1 1 1 1 1 0 nc l n = 4 60 c0 1 1 0 0 0 0 0 0 nc nc n = 5 61 c2 1 1 0 0 0 0 1 0 nc h n = 6 62 c4 1 1 0 0 0 1 0 0 h l n = 7 63 c6 1 1 0 0 0 1 1 0 h nc n = 8 64 c8 1 1 0 0 1 0 0 0 h h h = tie to v dd33 , nc = no connect = open or float, l = tie to gnd, x = dont care *mfr_i2c_base_address = 7bit 0x5c (factory default) operation slave address command code data byte wr a a a p 2974 f03 s 7 8 8 1 1 1 1 1 1 slave address command code data byte low wr a a a p 2974 f04 s 7 8 8 1 data byte high 8 1 1 1 1 1 1 a slave address command code data byte wr a a a p 2974 f05 s 7 8 8 1 pec 8 1 1 1 1 1 1 a figure 3. write byte protocol figure 2. pmbus packet protocol diagram element key figure 4. write word protocol figure 5. write byte protocol with pec slave address data byte wr a a p 2974 f02 s 7 s start condition sr repeated start condition rd read (bit value of 1) wr write (bit value of 0) x shown under a field indicates that that field is required to have the value of x a acknowledge (this bit position may be 0 for an ack or 1 for a nack) p stop condition pec packet error code master to slave slave to master continuation of protocol 8 1 1 1 x x 1 1 ...
ltc2974 21 2974fa for more information www.linear.com/ltc2974 slave address command code data byte low wr a a a p 2974 f06 s 7 8 8 1 data byte high 8 pec 8 1 1 1 1 1 1 1 a a figure 6. write word protocol with pec slave address wr a a p 2974 f07 s 7 8 1 1 1 1 1 command code figure 7. send byte protocol operation slave address command code pec wr a a a p 2974 f08 s 7 8 8 1 1 1 1 1 1 figure 8. send byte protocol with pec slave address command code slave address wr a a s 7 8 7 1 byte count = n 8 1 1 1 1 sr 1 1 a 1 rd a ? ? ? ? ? ? a p 2974 f13 data byte n 8 1 1 1 a data byte 1 8 data byte 2 8 1 1 a slave address command code slave address wr a a a p 2974 f09 s 7 8 7 1 data byte low 8 data byte high 8 1 1 1 1 sr 1 1 1 1 a 1 rd a 1 slave address command code slave address wr a a a pa 2974 f10 s 7 8 7 1 data byte low 8 data byte high pec 8 8 1 1 1 1 1 1 11 1 sr 1 a 1 rd a slave address command code slave address wr a a sr p 2974 f11 s 7 8 7 11 data byte 8 1 1 1 1 1 1 1 1 a rd a slave address command code slave address wr a a sr p 2974 f12 s 7 8 7 11 data byte 8 1 1 1 1 1 1 1 1 a rd a 1 a pec figure 12. read byte protocol with pec figure 9. read word protocol figure 10. read word protocol with pec figure 11. read byte protocol figure 13. block read a p 2974 f14 pec 8 1 1 1 slave address command code slave address wr a a s 7 8 7 1 byte count = n 8 1 1 1 1 sr 1 1 a 1 rd a ? ? ? ? ? ? a data byte n 8 1 a data byte 1 8 data byte 2 8 1 1 a figure 14. block read with pec
ltc2974 22 2974fa for more information www.linear.com/ltc2974 summary table command name cmd code description type paged data format units eeprom default value: float hex ref page page 0x00 channel or page currently selected for any command that supports paging. r/w byte n reg 0x00 28 operation 0x01 operating mode control. on/off, margin high and margin low. r/w byte y reg y 0x00 30 on_off_config 0x02 control pin and pmbus on/off command setting. r/w byte y reg y 0x12 30 clear_faults 0x03 clear any fault bits that have been set. send byte y na 61 write_protect 0x10 level of protection provided by the device against accidental changes. r/w byte n reg y 0x00 28 store_user_all 0x15 store entire operating memory to eeprom. send byte n na 40 restore_user_all 0x16 restore entire operating memory from eeprom. send byte n na 40 capability 0x19 summary of pmbus optional communication protocols supported by this device. r byte n reg 0xb0 78 vout_mode 0x20 output voltage data format and mantissa exponent (2 C13 ). r byte y reg 0x13 44 vout_command 0x21 servo target. nominal dc/dc converter output voltage setpoint. r/w word y l16 v y 1.0 0x2000 44 vout_max 0x24 upper limit on the output voltage the unit can command regardless of any other commands. r/w word y l16 v y 4.0 0x8000 44 vout_margin_high 0x25 margin high dc/dc converter output voltage setting. r/w word y l16 v y 1.05 0x219a 44 vout_margin_low 0x26 margin low dc/dc converter output voltage setting. r/w word y l16 v y 0.95 0x1e66 44 vin_on 0x35 input voltage (v in_sns ) above which power conversion can be enabled. r/w word n l11 v y 10.0 0xd280 43 vin_off 0x36 input voltage (v in_sns ) below which power conversion is disabled. all v out_en pins go off immediately or sequence off after toff_delay (see mfr_config_track_ enn). r/w word n l11 v y 9.0 0xd240 43 iout_cal_gain 0x38 the nominal resistance of the current sense element in m?. r/w word y l11 m y 1.0 0xba00 46 vout_ov_fault_limit 0x40 output overvoltage fault limit. r/w word y l16 v y 1.1 0x2333 44 vout_ov_fault_response 0x41 action to be taken by the device when an output overvoltage fault is detected. r/w byte y reg y 0x80 54 vout_ov_warn_limit 0x42 output overvoltage warning limit. r/w word y l16 v y 1.075 0x2266 44 vout_uv_warn_limit 0x43 output undervoltage warning limit. r/w word y l16 v y 0.925 0x1d9a 44 vout_uv_fault_limit 0x44 output undervoltage fault limit. used for ton_max_fault and power good de- assertion. r/w word y l16 v y 0.9 0x1ccd 44 pmbus command summary note: the data format abbreviations are detailed at the end of this table
ltc2974 23 2974fa for more information www.linear.com/ltc2974 summary table command name cmd code description type paged data format units eeprom default value: float hex ref page vout_uv_fault_response 0x45 action to be taken by the device when an output undervoltage fault is detected. r/w byte y reg y 0x7f 54 iout_oc_fault_limit 0x46 output overcurrent fault limit. r/w word y l11 a y 10.0 0xd280 46 iout_oc_fault_response 0x47 action to be taken by the device when an output overcurrent fault is detected. r/w byte y reg y 0x00 54 iout_oc_warn_limit 0x4a output overcurrent warning limit. r/w word y l11 a y 5.0 0xca80 46 iout_uc_fault_limit 0x4b output undercurrent fault limit. used to detect a reverse current and must be a negative value. r/w word y l11 a y -1.0 0xbe00 46 iout_uc_fault_response 0x4c action to be taken by the device when an output undercurrent fault is detected. r/w byte y reg y 0x00 54 ot_fault_limit 0x4f overtemperature fault limit for the external temperature sensor. r/w word y l11 c y 65.0 0xea08 48 ot_fault_response 0x50 action to be taken by the device when an overtemperature fault is detected on the external temperature sensor. r/w byte y reg y 0xb8 54 ot_warn_limit 0x51 overtemperature warning limit for the external temperature sensor r/w word y l11 c y 60.0 0xe3c0 48 ut_warn_limit 0x52 undertemperature warning limit for the external temperature sensor. r/w word y l11 c y 0 0x8000 48 ut_fault_limit 0x53 undertemperature fault limit for the external temperature sensor. r/w word y l11 c y C5.0 0xcd80 48 ut_fault_response 0x54 action to be taken by the device when an undertemperature fault is detected on the external temperature sensor. r/w byte y reg y 0xb8 54 vin_ov_fault_limit 0x55 input overvoltage fault limit measured at vin_sns pin. r/w word n l11 v y 15.0 0xd3c0 43 vin_ov_fault_response 0x56 action to be taken by the device when an input overvoltage fault is detected. r/w byte n reg y 0x80 54 vin_ov_warn_limit 0x57 input overvoltage warning limit measured at vin_sns pin. r/w word n l11 v y 14.0 0xd380 43 vin_uv_warn_limit 0x58 input undervoltage warning limit measured at vin_sns pin. r/w word n l11 v y 0 0x8000 43 vin_uv_fault_limit 0x59 input undervoltage fault limit measured at vin_sns pin. r/w word n l11 v y 0 0x8000 43 vin_uv_fault_response 0x5a action to be taken by the device when an input undervoltage fault is detected. r/w byte n reg y 0x00 54 power_good_on 0x5e output voltage at or above which a power good should be asserted. r/w word y l16 v y 0.96 0x1eb8 44 power_good_off 0x5f output voltage at or below which a power good should be de-asserted when mfr_ config_all_pwrgd_off_uses_uv is clear. r/w word y l16 v y 0.94 0x1e14 44 pmbus command summary
ltc2974 24 2974fa for more information www.linear.com/ltc2974 pmbus command summary summary table command name cmd code description type paged data format units eeprom default value: float hex ref page ton_delay 0x60 time from control pin and/or operation command = on to v out_en pin = on. r/w word y l11 ms y 1.0 0xba00 51 ton_rise 0x61 time from when the v out_enn pin goes high until the ltc2974 optionally soft- connects its dac and begins to servo the output voltage to the desired value. r/w word y l11 ms y 10.0 0xd280 51 ton_max_fault_limit 0x62 maximum time from v out_en pin on assertion that an uv condition will be tolerated before a ton_max_fault condition results. r/w word y l11 ms y 15.0 0xd3c0 51 ton_max_fault_response 0x63 action to be taken by the device when a ton_max_fault event is detected. r/w byte y reg y 0xb8 54 toff_delay 0x64 time from control pin and/or operation command = off to v out_en pin = off. r/w word y l11 ms y 1.0 0xba00 51 status_byte 0x78 one byte summary of the units fault condition. r byte y reg na 61 status_word 0x79 two byte summary of the units fault condition. r word y reg na 61 status_vout 0x7a output voltage fault and warning status. r byte y reg na 61 status_iout 0x7b output current fault and warning status. r byte y reg na 61 status_input 0x7c input supply fault and warning status. r byte n reg na 61 status_temperature 0x7d external temperature fault and warning status for read_temperature_1. r byte y reg na 61 status_cml 0x7e communication and memory fault and warning status. r byte n reg na 61 status_mfr_specific 0x80 manufacturer specific fault and state information. r byte y reg na 61 read_vin 0x88 input supply voltage. r word n l11 v na 66 read_vout 0x8b dc/dc converter output voltage. r word y l16 v na 66 read_iout 0x8c dc/dc converter output current. r word y l11 a na 66 read_temperature_1 0x8d external diode junction temperature. this is the value used for all temperature related processing, including iout_cal_ gain. r word y l11 c na 66 read_temperature_2 0x8e internal junction temperature. r word n l11 c na 66 read_pout 0x96 dc/dc converter output power. r word y l11 w na 66 pmbus_revision 0x98 pmbus revision supported by this device. current revision is 1.1. r byte n reg 0x11 78 user_data_00 0xb0 manufacturer reserved for ltpowerplay. r/w word n reg y n/a 79 user_data_01 0xb1 manufacturer reserved for ltpowerplay. r/w word y reg y n/a 79 user_data_02 0xb2 oem reserved. r/w word n reg y n/a 79
ltc2974 25 2974fa for more information www.linear.com/ltc2974 summary table command name cmd code description type paged data format units eeprom default value: float hex ref page user_data_03 0xb3 scratchpad location. r/w word y reg y 0x00 79 user_data_04 0xb4 scratchpad location. r/w word n reg y 0x00 79 mfr_ltc_reserved_1 0xb5 manufacturer reserved. r/w word y reg y na 79 mfr_t_self_heat 0xb8 calculated temperature rise due to self-heating of output current sense device above value measured by external temperature sensor. r word y l11 c na 48 mfr_iout_cal_gain_tau_ inv 0xb9 inverse of time constant for mfr_t_self_ heat changes scaled by 4 ? t conv_sense . r/w word y l11 y 0.0 0x8000 48 mfr_iout_cal_gain_theta 0xba thermal resistance from inductor core to point measured by external temperature sensor. r/w word y l11 c/w y 0.0 0x8000 48 mfr_read_iout 0xbb alternate data format for read_iout. one lsb = 2.5ma. r word y cf 2.5ma na 66 mfr_ltc_reserved_2 0xbc manufacturer reserved. r/w word y reg na 79 mfr_ee_unlock 0xbd unlock user eeprom for access by mfr_ee_erase and mfr_ee_data commands. r/w byte n reg na 40 mfr_ee_erase 0xbe initialize user eeprom for bulk programming by mfr_ee_data. r/w byte n reg na 40 mfr_ee_data 0xbf data transferred to and from eeprom using sequential pmbus word reads or writes. supports bulk programming. r/w word n reg na 40 mfr_config_ltc2974 0xd0 configuration bits that are channel specific. r/w word y reg y 0x0080 30 mfr_config_all_ltc2974 0xd1 configuration bits that are common to all pages. r/w word n reg y 0x0f7b 30 mfr_faultb0_propagate 0xd2 configuration that determines if a channels faulted off state is propagated to the faultb0 pin. r/w byte y reg y 0x00 59 mfr_faultb1_propagate 0xd3 configuration that determines if a channels faulted off state is propagated to the faultb1 pin. r/w byte y reg y 0x00 59 mfr_pwrgd_en 0xd4 configuration that maps wdi/resetb status and individual channel power good to the pwrgd pin. r/w word n reg y 0x0000 52 mfr_faultb0_response 0xd5 action to be taken by the device when the faultb0 pin is asserted low. r/w byte n reg y 0x00 59 mfr_faultb1_response 0xd6 action to be taken by the device when the faultb1 pin is asserted low. r/w byte n reg y 0x00 59 mfr_iout_peak 0xd7 maximum measured value of read_iout. r word y l11 a na 66 mfr_iout_min 0xd8 minimum measured value of read_iout. r word y l11 a na 66 mfr_config2_ltc2974 0xd9 configuration bits that are channel specific r/w byte n reg y 0x00 30 pmbus command summary
ltc2974 26 2974fa for more information www.linear.com/ltc2974 summary table command name cmd code description type paged data format units eeprom default value: float hex ref page mfr_config3_ltc2974 0xda configuration bits that are channel specific r/w byte n reg y 0x00 30 mfr_retry_delay 0xdb retry interval during fault retry mode. r/w word n l11 ms y 200 0xf320 54 mfr_restart_delay 0xdc delay from actual control active edge to virtual control active edge. r/w word n l11 ms y 400 0xfb20 51 mfr_vout_peak 0xdd maximum measured value of read_vout. r word y l16 v na 66 mfr_vin_peak 0xde maximum measured value of read_vin. r word n l11 v na 66 mfr_temperature_1_peak 0xdf maximum measured value of read_ temperature_1. r word y l11 c na 66 mfr_dac 0xe0 manufacturer register that contains the code of the 10-bit dac. r/w word y reg n 0x0000 44 mfr_powergood_ assertion_delay 0xe1 power-good output assertion delay. r/w word n l11 ms y 100 0xeb20 52 mfr_watchdog_t_first 0xe2 first watchdog timer interval. r/w word n l11 ms y 0 0x8000 52 mfr_watchdog_t 0xe3 watchdog timer interval. r/w word n l11 ms y 0 0x8000 52 mfr_page_ff_mask 0xe4 configuration defining which channels respond to global page commands (page=0xff). r/w byte n reg y 0xf 28 mfr_pads 0xe5 current state of selected digital i/o pads. r/w word n reg na 61 mfr_i2c_base_address 0xe6 base value of the i 2 c/smbus address byte. r/w byte n reg y 0x5c 28 mfr_special_id 0xe7 manufacturer code for identifying the ltc2974. r word n reg y 0x0213 78 mfr_special_lot 0xe8 customer dependent codes that identify the factory programmed user configuration stored in eeprom. contact factory for default value. r byte y reg y 78 mfr_vout_discharge_ threshold 0xe9 coefficient used to multiply vout_ command in order to determine v out off threshold voltage. r/w word y l11 y 2.0 0xc200 44 mfr_fault_log_store 0xea command a transfer of the fault log from ram to eeprom. send byte n na 70 mfr_fault_log_restore 0xeb command a transfer of the fault log previously stored in eeprom back to ram. send byte n na 70 mfr_fault_log_clear 0xec initialize the eeprom block reserved for fault logging and clear any previous fault logging locks. send byte n na 70 mfr_fault_log_status 0xed fault logging status. r byte n reg y na 70 mfr_fault_log 0xee fault log data bytes. this sequentially retrieved data is used to assemble a complete fault log. r block n reg y na 70 pmbus command summary
ltc2974 27 2974fa for more information www.linear.com/ltc2974 summary table command name cmd code description type paged data format units eeprom default value: float hex ref page mfr_common 0xef manufacturer status bits that are common across multiple ltc chips. r byte n reg na 61 mfr_iout_cal_gain_tc 0xf6 temperature coefficient applied to iout_ cal_gain. r/w word y cf ppm y 0x0 46 mfr_retry_count 0xf7 retry count for all faulted off conditions that enable retry. r/w byte n reg y 0x00 54 mfr_temp_1_gain 0xf8 inverse of external diode temperature non ideality factor. one lsb = 2 C14 . r/w word y cf y 1 0x4000 48 mfr_temp_1_offset 0xf9 offset value for the external temperature. r/w word y l11 c y 0 0x8000 48 mfr_iout_sense_voltage 0xfa absolute value of v isensep C v isensem . one lsb = 3.05v. r word y cf 3.05v na 66 mfr_vout_min 0xfb minimum measured value of read_vout. r word y l16 v na 66 mfr_vin_min 0xfc minimum measured value of read_vin. r word n l11 v na 66 mfr_temperature_1_min 0xfd minimum measured value of read_ temperature_1. r word y l11 c na 66 pmbus command summary data formats l11 linear_5s_11s pmbus data field b[15:0] value = y ? 2 n where n = b[15:11] is a 5-bit twos complement integer and y = b[10:0] is an 11-bit twos complement integer example: read_vin = 10v for b[15:0] = 0xd280 = 1101_0010_1000_0000b value = 640 ? 2 C6 = 10 see pmbus spec part ii: paragraph 7.1 l16 linear_16u pmbus data field b[15:0] value = y ? 2 n where y = b[15:0] is an unsigned integer and n = vout_mode_parameter is a 5-bit twos complement exponent that is hardwired to C13 decimal. example: vout_command = 4.75v for b[15:0] = 0x9800 = 1001_1000_0000_0000b value = 38912 ? 2 C13 = 4.75 see pmbus spec part ii: paragraph 8.3.1 reg register pmbus data field b[15:0] or b[7:0]. bit field meaning is defined in detailed pmbus command register description. cf custom format pmbus data field b[15:0] value is defined in detailed pmbus command register description. this is often an unsigned or twos complement integer scaled by an mfr specific constant.
ltc2974 28 2974fa for more information www.linear.com/ltc2974 addressing and write protect command name cmd code description type paged format units eeprom default value ref page page 0x00 channel or page currently selected for any command that supports paging. r/w byte n reg 0x00 28 write_protect 0x10 level of protection provided by the device against accidental changes. r/w byte n reg y 0x00 28 mfr_i2c_base_address 0xe6 base value of the i 2 c/smbus address byte. r/w byte n reg y 0x5c 29 mfr_page_ff_mask 0xe4 configuration defining which channels respond to global page commands (page=0xff). r/w byte n reg y 0xf 29 pmbus command description page the ltc2974 has four pages that correspond to the four dc/dc converter channels that can be managed. each dc/dc converter channel can be uniquely programmed by first setting the appropriate page. setting page = 0xff allows a simultaneous write to all pages for pmbus commands that support global page pro - gramming. the only commands that support page = 0xff are clear_faults, operation and on_off_config. see mfr_page_ff_mask for additional options. reading any paged pmbus register with page = 0xff returns un - predictable data and will trigger a cml fault. writes to pages that do not support page = 0xff with page = 0xff will be ignored and generate a cml fault. page data contents bit(s) symbol operation b[7:0] page page operation. 0x00: all pmbus commands address channel/page 0. 0x01: all pmbus commands address channel/page 1. 0x02: all pmbus commands address channel/page 2. 0x03: all pmbus commands address channel/page 3. 0xxx: all non specified values reserved. 0xff: a single pmbus write/send to commands that support this mode will simultaneously address all channel/pages with mfr_page_ff_mask enabled. write_protect the write_protect command provides protection against accidental programming of the ltc2974 command reg - isters. all supported commands may have their parameters read, regardless of the write_protect setting, and the eeprom contents can also be read regardless of the write_protect settings. there are two levels of protection: ? level 1: nothing can be changed except the level of write protection itself. values can be read from all pages. this setting can be stored to eeprom. ? level 2: nothing can be changed except for the level of protection, channel on/off state, and clearing of faults. values can be read from all pages. this setting can be stored to eeprom.
ltc2974 29 2974fa for more information www.linear.com/ltc2974 write_protect data contents bit(s) symbol operation b[7:0] write_protect[7:0] 1000_0000b: level 1 protection - disable all writes except to the write_protect, page, mfr_ee_unlock, and store_ user_all commands. 0100_0000b: level 2 protection C disable all writes except to the write_protect, page, mfr_ee_unlock, store_ user_all, operation, mfr_page_ff_mask and clear_faults commands. 0000_0000b: enable writes to all commands. xxxx_xxxxb: all other values reserved. write-protect pin the wp pin allows the user to write-protect the ltc2974s configuration registers. the wp pin is active high, and when asserted it provides level 2 protection: all writes are disabled except to the write_protect, page, mfr_ee_unlock, store_user_all, operation, mfr_page_ff_mask and clear_faults commands. the most restrictive setting between the wp pin and write_protect command will override. for example if wp = 1 and write_protect = 0x80, then the write_protect command overrides, since it is the most restrictive. mfr_page_ff_mask the mfr_page_ff_mask command is used to select which channels respond when the global page command (page=0xff) is in use. mfr_page_ff_mask data contents bit(s) symbol operation b[7:4] reserved always returns 0000b b[3] mfr_page_ff_mask_chan3 channel 3 masking of global page command (page=0xff) accesses 0 = ignore global page command accesses 1 = fully respond to global page command accesses b[2] mfr_page_ff_mask_chan2 channel 2 masking of global page command (page=0xff) accesses 0 = ignore global page command accesses 1 = fully respond to global page command accesses b[1] mfr_page_ff_mask_chan1 channel 1 masking of global page command (page=0xff) accesses 0 = ignore global page command accesses 1 = fully respond to global page command accesses b[0] mfr_page_ff_mask_chan0 channel 0 masking of global page command (page=0xff) accesses 0 = ignore global page command accesses 1 = fully respond to global page command accesses mfr_i2c_base_address the mfr_i2c_base_address command determines the base value for the i 2 c/smbus address byte. offsets of 0 to 9 are added to this base address to generate the device i 2 c/smbus address. the part responds to the device address. mfr_i2c_base_address data contents bit(s) symbol operation b[7] reserved read only, always returns 0. b[6:0] i2c_base_address this 7-bit value determines the base value of the 7-bit i 2 c/smbus address. see operation section: device address. pmbus command description
ltc2974 30 2974fa for more information www.linear.com/ltc2974 operation the operation command is used to turn the unit on and off in conjunction with the control pin and on_off_con - fig. this command register responds to the global page command (page=0xff). the contents and functions of the data byte are shown in the following tables. a minimum t off_min wait time must be observed between any operation commands used to turn the unit off and then back on to give the adc telemetry loop time to complete a full cycle. operation data contents (on_off_config_use_pmbus=1) symbol action operation_control[1:0] operation_margin[1:0] operation_fault[1:0] reserved (read only) bits b[7:6] b[5:4] b[3:2] b[1:0] function turn off immediately 00 xx xx 00 sequence on 10 00 xx 00 margin low (ignore faults and warnings) 10 01 01 00 margin low 10 01 10 00 margin high (ignore faults and warnings 10 10 01 00 margin high 10 10 10 00 sequence off with margin to nominal 01 00 xx 00 sequence off with margin low (ignore faults and warnings) 01 01 01 00 sequence off with margin low 01 01 10 00 sequence off with margin high (ignore faults and warnings) 01 10 01 00 sequence off with margin high 01 10 10 00 reserved all remaining combinations pmbus command description on/off control, margining and configuration command name cmd code description type paged format units eeprom default value ref page operation 0x01 operating mode control. on/off, margin high and margin low. r/w byte y reg y 0x00 30 on_off_config 0x02 control pin and pmbus on/off command setting. r/w byte y reg y 0x12 31 mfr_config_ltc2974 0xd0 configuration bits that are channel specific. r/w word y reg y 0x0080 32 mfr_config2_ltc2974 0xd9 configuration bits that are channel specific r/w byte n reg y 0x00 35 mfr_config3_ltc2974 0xda configuration bits that are channel specific r/w byte n reg y 0x00 35 mfr_config_all_ltc2974 0xd1 configuration bits that are common to all pages. r/w word n reg y 0x0f7b 39
ltc2974 31 2974fa for more information www.linear.com/ltc2974 operation data contents (on_off_config_use_pmbus=0) on or off symbol action operation_control[1:0] operation_margin[1:0] operation_fault[1:0] reserved (read only) bits b[7:6] b[5:4] b[3:2] b[1:0] function output at nominal 00, 01 or 10 00 xx 00 margin low (ignore faults and warnings) 00, 01 or 10 01 01 00 margin low 00, 01 or 10 01 10 00 margin high (ignore faults and warnings 00, 01 or 10 10 01 00 margin high 00, 01 or 10 10 10 00 reserved all remaining combinations on_off_config the on_off_config command configures the combination of control pin input and pmbus commands needed to turn the ltc2974 on/off, including the power-on behavior, as shown in the following table. this command register responds to the global page command (page=0xff). after the part has initialized, an additional comparator monitors vin_sns. the vin_on threshold must be exceeded before the output power sequencing can begin. after v in is initially applied, the part will typically require t init time to initialize and begin the ton_delay timer. the readback of voltages and currents may require an additional wait for tupdate_adc. a minimum t off_min wait time must be observed for any control pin toggle used to turn the unit off and then back on. on_off_config data contents bit(s) symbol operation b[7:5] reserved dont care. always returns 0. b[4] on_off_config_controlled_on control default autonomous power up operation. 0: unit powers up regardless of the control pin or operation value. unit always powers up with sequencing. to turn unit on without sequencing, set ton_delay = 0. 1: unit does not power up unless commanded by the control pin and/or the operation command on the serial bus. if on_off_config[3:2] = 00, the unit never powers up. b[3] on_off_config_use_pmbus controls how the unit responds to commands received via the serial bus. 0: unit ignores the operation_control[1:0]. 1: unit responds to operation_control[1:0]. depending on on_off_config_use_control, the unit may also require the control pin to be asserted for the unit to start. b[2] on_off_config_use_control controls how unit responds to the control pin. 0: unit ignores the control pin. 1: unit requires the control pin to be asserted to start the unit. depending on on_off_config_use_pmbus the operation command may also be required to instruct the device to start. b[1] reserved not supported. always returns 1. b[0] on_off_config_control_fast_off control pin turn off action when commanding the unit to turn off 0: use the programmed toff_delay. 1: turn off the output and stop transferring energy as quickly as possible. the device does not sink current in order to decrease the output voltage fall time. pmbus command description
ltc2974 32 2974fa for more information www.linear.com/ltc2974 mfr_config_ltc2974 this command is used to configure various manufacturer specific operating parameters for each channel. mfr_config_ltc2974 data contents bit(s) symbol operation b[15] reserved dont care. always returns 0. b[14] mfr_config_cascade_on configures channels control pin for cascade sequence on. there is no provision for cascade sequence off. see description for time based sequence off options. b[13:12] mfr_config_controln_sel[1:0] selects the active control pin input (control0 , control1, control2 or control3) for this channel. 0: select control0 pin. 1: select control1 pin. 2: select control2 pin. 3: select control3 pin. b[11] mfr_config_fast_servo_off disables fast servo when margining or trimming output voltages: 0: fast-servo enabled. 1: fast-servo disabled. b[10] mfr_config_supervisor_resolution selects voltage supervisor resolution: 0: high resolution = 4mv / lsb, range for v vsensepn C v vsensemn is 0 to 3.8v 1: low resolution = 8mv / lsb, range for v vsensepn C v vsensemn is 0 to 6.0v b[9:8] reserved always returns 0. b[7] mfr_config_servo_continuous select whether the unit should continuously servo vout after it has reached a new margin or nominal target. only applies when mfr_ config _dac_mode = 00b. 0: do not continuously servo vout after reaching initial target. 1: continuously servo vout to target. b[6] mfr_config_servo_on_warn control re-servo on warning feature. only applies when mfr_config_dac_mode = 00b and mfr_config_ servo_continuous = 0. 0: do not allow the unit to re-servo when a vout warning threshold is met or exceeded. 1: allow the unit to re-servo vout to nominal target if vout v(vout_ov_warn_limit) or vout v(vout_uv_warn_limit). b[5:4] mfr_config_dac_mode determines how dac is used when channel is in the on state and ton_rise has elapsed. 00: soft-connect (if needed) and servo to target. 01: dac not connected. 10: dac connected immediately using value from mfr_dac command. if this is the configuration after a reset or restore_user_all, mfr_dac will be undefined and must be written to desired value. 11: dac is soft-connected. after soft-connect is complete mfr_dac may be written. b[3] mfr_config_vo_en_wpu_en v out_en pin charge-pumped, current-limited pull-up enable. 0: disable weak pull-up. v out_en pin driver is three-stated when channel is on. 1: use weak current-limited pull-up on v out_en pin when the channel is on. b[2] mfr_config_vo_en_wpd_en v out_en pin current-limited pull-down enable. 0: use a fast n-channel device to pull down v out_en pin when the channel is off for any reason. 1: use weak current-limited pull-down to discharge v out_en pin when channel is off due to soft stop by the control pin and/or operation command. if the channel is off due to a fault, use the fast pull-down on the v out_en pin. pmbus command description
ltc2974 33 2974fa for more information www.linear.com/ltc2974 mfr_config_ltc2974 data contents bit(s) symbol operation b[1] mfr_config_dac_gain dac buffer gain. 0: select dac buffer gain dac_gain_0 (1.38v full-scale) 1: select dac buffer gain dac_gain_1 (2.65v full-scale) b[0] mfr_config_ dac_pol dac output polarity. 0: encodes negative (inverting) dc/dc converter trim input. 1: encodes positive (non-inverting) dc/dc converter trim input. cascade sequence on with time-based sequence off cascade sequence on allows a master power supply to sequence on a series of slave supplies by connecting each power supplys power good output to the control pin of the next power supply in the chain. please note that the power good signal is that of the power supply and not derived from the ltc2974s internal power good processing. power good based cascade sequence off is not supported, off sequencing must be managed using immediate or time based sequence off. see also tracking based sequencing. cascade sequence on is illustrated in figure 15. for each slave channel mfr_config_cascade_on is asserted high and the associated control input is connected to the power good output of the previous power supply. in this configuration each slave channels startup is delayed until the previous supply has powered up. cascade sequence off is not directly supported. options for reversing the sequence when turning the supplies off include: ? using the operation command to turn off all the channels with an appropriate off delay . ? using the fault pin to bring all the channels down immediately or in sequence with an appropriate off delay. when asserted, mfr_config_cascade_on enables a slave channel to honor fault retries even when its control pin is low. additionally, if the system has faulted off after zero or a finite number of retries, an operation command may pmbus command description figure 15. ltc2974 configured to cascade sequence on and time-base sequence off v outp run v outm v sensep0 v sensem0 powergood0 faultb0 faultb0 ltc2974 slaves master control0 recommended connection when hardware on/off control is required v out_en0 control1 control0 dc/dc load v outp run v outm v sensep1 v sensem1 powergood1 v out_en1 control2 dc/dc load v outp run v outm v sensep2 v sensem2 powergood2 v out_en2 control3 dc/dc load to next control pin v outp run v outm v sensep3 v sensem3 powergood3 v out_en3 dc/dc load 2974 f15
ltc2974 34 2974fa for more information www.linear.com/ltc2974 pmbus command description figure 16. cascade sequence on with time based sequence down on fault0 be used to turn all cascade channels off then on to clear the faulted off state when the slaves control pin is low. for this reason we refer to the control pin as being redefined as a sequence pin. the waveform of figure 16 illustrates cascade sequence on and time based sequence off using the configuration illustrated in figure 15. in this example the faultb0 pin is used as a broadcast off signal. turning the system off with the faultb0 requires all slave channels to be configured with mfr_faultb0_response_chan n asserted high. after the system is turned off, the ltc2974 will assert alertb with all slave channels indicating a status_mfr_fault0_in event. v out2 v out3 powergood3 2974 f16 powergood2 powergood1 powergood0 control-faultb0 v out1 v out0 toff_delay3 toff_delay2 toff_delay1 toff_delay0
ltc2974 35 2974fa for more information www.linear.com/ltc2974 pmbus command description mfr_config2_ltc2974 this command register determines whether v out overvoltage or overcurrent faults from a given channel cause the auxfaultb pin to be pulled low. mfr_config2_ltc2974 data contents bit(s) symbol operation b[7] mfr_auxfaultb_oc_fault_response_ chan3 response to channel 3 iout_oc_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[6] mfr_auxfaultb_oc_fault_response_ chan2 response to channel 2 iout_oc_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[5] mfr_auxfaultb_oc_fault_response_ chan1 response to channel 1 iout_oc_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[4] mfr_auxfaultb_oc_fault_response_ chan0 response to channel 0 iout_oc_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[3] mfr_auxfaultb_ov_fault_response_ chan3 response to channel 3 vout_ov_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[2] mfr_auxfaultb_ov_fault_response_ chan2 response to channel 2 vout_ov_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[1] mfr_auxfaultb_ov_fault_response_ chan1 response to channel 1 vout_ov_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[0] mfr_auxfaultb_ov_fault_response_ chan0 response to channel 0 vout_ov_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. mfr_config3_ltc2974 this command register determines whether v out undercurrent faults from a given channel cause the auxfaultb pin to be pulled low. this command also allows tracking to be enabled on any channel. mfr_config3_ltc2974 data contents bit(s) symbol operation b[7] mfr_auxfaultb_uc_fault_response_ chan3 response to channel 3 iout_uc_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[6] mfr_auxfaultb_uc_fault_response_ chan2 response to channel 2 iout_uc_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low.
ltc2974 36 2974fa for more information www.linear.com/ltc2974 pmbus command description b[5] mfr_auxfaultb_uc_fault_response_ chan1 response to channel 1 iout_uc_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[4] mfr_auxfaultb_uc_fault_response_ chan0 response to channel 0 iout_uc_fault. 1 = pull auxfaultb low via fast pull-down. 0 = do not pull auxfaultb low. b[3] mfr_track_en_chan3 select if channel 3 is a slave in a tracked power supply system. 0: channel is not a slave in a tracked power supply system. 1: channel is a slave in a tracked power supply system. b[2] mfr_track_en_chan2 select if channel 2 is a slave in a tracked power supply system. 0: channel is not a slave in a tracked power supply system. 1: channel is a slave in a tracked power supply system. b[1] mfr_track_en_chan1 select if channel 1 is a slave in a tracked power supply system. 0: channel is not a slave in a tracked power supply system. 1: channel is a slave in a tracked power supply system. b[0] mfr_track_en_chan0 select if channel 0 is a slave in a tracked power supply system. 0: channel is not a slave in a tracked power supply system. 1: channel is a slave in a tracked power supply system. figure 17. ltc2974 configured to control, supervise and monitor power supplies equipped with tracking pin v outp run v outm v sensep0 v sensem0 track faultb0 faultb0 ltc2974 control0 v out_en0 control0 dc/dc load v outp run v outm v sensep1 v sensem1 track v out_en1 dc/dc load v outp run v outm v sensep2 v sensem2 track v out_en2 dc/dc load v outp run v outm v sensep3 v sensem3 track v fb v dac0 v fb v dac1 v dac3 v fb v dac2 v fb v out_en3 dc/dc load 2974 f17 r2_3 r1_3 r2_2 r1_2 r2_1 r1_1
ltc2974 37 2974fa for more information www.linear.com/ltc2974 figure 18. control pin tracking all supplies up and down figure 19. fault on channel 1 tracking all supplies down tracking supplies on and off the ltc2974 supports tracking power supplies that are equipped with a tracking pin and configured for tracking. a tracking power supply uses a secondary feedback terminal (track) to allow its output voltage to be scaled to an external master voltage. typically the external voltage is generated by the supply with the highest voltage in the sys - tem, which is fed to the slave track pins (see figure 17). supplies that track a master supply must be enabled before the master supply comes up and disabled after the master supply comes down. enabling the slave supplies when the master is down requires supervisors monitoring the slaves to disable uv detection. slave uc detection must also be pmbus command description v out2 v out3 vout_en(3:1) 2974 f19 vout_en0 faultb0 control uv fault on channel 1 brings down master via faultb0. all slave channels including the one with the uv fault enter toff_delay slave output enables turn on first slave output enables turn off last master brings down next highest slave ton_rise expires for all channels. uv and uc detect enabled on all channels toff_delay entered for all channels. uv and uc detect disabled on all channels v out1 v out0 v out2 v out3 vout_en(3:1) 2974 f18 vout_en0 control slave output enables turn on first slave output enables turn off last master brings down next highest slave ton_rise expires for all channels. uv and uc detect enabled on all channels toff_delay entered for all channels. uv and uc detect disabled on all channels v out1 v out0
ltc2974 38 2974fa for more information www.linear.com/ltc2974 disabled when the slaves are tracking the master down to prevent false uc events. all channels configured for track - ing must track off together in response to a fault on any channel or any other condition that can bring one or more of the channels down. prematurely disabling a slave channel via its run pin may cause that channel to shut down out of sequence (see figure 20) an important feature of the ltc2974 is the ability to control, monitor and supervise dc/dc converters that are config - ured to track a master supply on and off. the ltc2974 supports the following tracking features: ? track channels on and off without issuing false uv/uc events when the slave channels are tracking up or down. ? track all channels down in response to a fault from a slave or master. ? track all channels down when vin_sns drops below vin_off, share clock is held low or restore_user_all is issued. ? ability to to reconfigure selected channels that are part of a tracking group to sequence up after the group has tracked up or sequence down before the group has tracked down. tracking implementation the ltc2974 supports tracking through the coordinated programing of ton_delay, ton_rise,toff_delay and mfr_track_ en_chann. the master channel must be configured to turn on after all the slave channels have turned on and to turn off before all the slave channels turn off. slaves that are enabled before the master will remain off until the tracking pin allows them to turn on. slaves will be turned off via the tracking pin even though their run pin is still asserted. ton_rise must be extended on the slaves so that it ends relative to the rise of the track pin and not the rise of the v out_en pin. when mfr_track_en_chann is enabled the channel is reconfigured to: ? sequence down on fault, vin_off, share_clk low or restore_user_all. ? ignore uv and uc during toff_delay. note that ignoring uv and uc during ton_rise and ton_max_fault always happens regardless of how this bit is set. pmbus command description figure 20. improperly configured fault response on faulting channel disrupts tracking v out2 v out3 vout_en(3:2) 2974 f20 vout_en1 vout_en0 faultb0 control uv fault on channel 1 brings down master via faultb0. all slaves with enabled run pins track down correctly slave output enables turn on first slave output enables turn off last disabling vout_en1 immediately in response to the uv fault causes vout1 to shut down out of sequence ton_rise expires for all channels. uv and uc detect enabled on all channels toff_delay entered for all channels. uv and uc detect disabled on all channels v out1 v out0
ltc2974 39 2974fa for more information www.linear.com/ltc2974 pmbus command description the following example illustrates configuring an ltc2974 with one master channel and three slaves. master channel 0 ton_delay = ton_delay_master ton_rise = ton_rise_master toff_delay = toff_delay_master mfr_track_en_chan0 = 0 slave channel n ton_delay = ton_delay_slave ton_rise = ton_delay_master + ton_rise_slave toff_delay = toff_delay_master + t_off_delay_slave mfr_track_en_chan0 = 1 where: ton_delay_master C ton_delay_slave > run to track setup time toff_delay_slave > time for master supply to fall. the system response to a control pin toggle is illustrated in figure 18. the system response to a uv fault on a slave channel is illustrated in figure 19. mfr_config_all_ltc2974 this command is used to configure parameters that are common to all channels on the ic. they may be set or reviewed from any page setting. mfr_config_all_ltc2974 data contents bit(s) symbol operation b[15:12] reserved dont care. always returns 0. b[11] mfr_config_all_pwrgd_off_uses_uv selects pwrgd de-assertion source for all channels. 0: pwrgd is de-asserted based on v out being below or equal to power_good_off. this option uses the adc. response time is approximately 100ms to 200ms. 1: pwrgd is de-asserted based on v out being below or equal to vout_uv_limit. this option uses the high speed supervisor. response time is approximately 12s. b[10] mfr_config_all_fast_fault_log controls number of adc readings completed before transferring fault log memory to eeprom. 0: all adc telemetry values will be updated before transferring fault log to eeprom. slower. 1: telemetry values will be transferred from fault log to eeprom within 24ms after detecting fault. faster. b[9] mfr_config_all_control3_pol selects active polarity of control3 pin 0: active low (pull pin low to start unit). 1: active high (pull pin high to start unit). b[8] mfr_config_all_control2_pol selects active polarity of control2 pin 0: active low (pull pin low to start unit). 1: active high (pull pin high to start unit).
ltc2974 40 2974fa for more information www.linear.com/ltc2974 mfr_config_all_ltc2974 data contents bit(s) symbol operation b[7] mfr_config_all_fault_log_enable enable fault logging to eeprom in response to fault. 0: fault logging to eeprom is disabled. 1: fault logging to eeprom is enabled. b[6] mfr_config_all_vin_on_clr_faults_en allow v in rising above vin_on to clear all latched faults. 0: vin_on clear faults feature is disabled. 1: vin_on clear faults feature is enabled. b[5] mfr_config_all_control1_pol selects active polarity of control1 pin 0: active low (pull pin low to start unit). 1: active high (pull pin high to start unit). b[4] mfr_config_all_control0_pol selects active polarity of control0 pin 0: active low (pull pin low to start unit). 1: active high (pull pin high to start unit). b[3] mfr_config_all_vin_share_enable allow this unit to hold share_clk pin low when v in has not risen above vin_on or has fallen below vin_off. when enabled this unit will also turn all channels off in response to share-clock being held low. 0: share_clk inhibit is disabled. 1: share_clk inhibit is enabled. b[2] mfr_config_all_pec_en pmbus packet error checking enable. 0: pec is accepted but not required. 1: pec is enabled. b[1] mfr_config_all_longer_pmbus_timeout increase pmbus timeout interval by a factor of 8. recommended for fault logging. 0: pmbus timeout is multiplied by a factor of 8. 1: pmbus timeout is not multiplied by a factor of 8. b[0] mfr_config_all_auxfaultb_wpu_dis auxfaultb charge-pumped, current-limited pull-up disable. 0: use weak current-limited pull-up on auxfaultb after power-up, as long as no faults have forced auxfaultb off. 1: disable weak pull-up. auxfaultb driver is tri-stated after power-up as long as no faults have forced auxfaultb off. pmbus command description programming user eeprom space command name cmd code description type paged format units eeprom default value ref page store_user_all 0x15 store entire operating memory to eeprom. send byte n na 41 restore_user_all 0x16 restore entire operating memory from eeprom. send byte n na 41 mfr_ee_unlock 0xbd unlock user eeprom for access by mfr_ee_erase and mfr_ee_data commands. r/w byte n reg na 41 mfr_ee_erase 0xbe initialize user eeprom for bulk programming by mfr_ee_data. r/w byte n reg na 42 mfr_ee_data 0xbf data transferred to and from eeprom using sequential pmbus word reads or writes. supports bulk programming. r/w word n reg na 42
ltc2974 41 2974fa for more information www.linear.com/ltc2974 store_user_all and restore_user_all store_user_all, restore_user_all commands provide access to user eeprom space. once a command is stored in user eeprom, it will be restored with explicit restore command or when the part emerges from power-on reset after power is applied. while either of these commands is being processed, the part will indicate it is busy, see response when part is busy on page 43. store_user_all. issuing this command will store all operating memory commands with a corresponding eeprom memory location. restore_user_all. issuing this command will restore all commands from eeprom memory. it is recommended that this command not be executed while a unit is enabled since all monitoring is suspended while the eeprom is transferred to operating memory, and intermediate values from eeprom may not be compatible with the values initially stored in operating memory. bulk programming the user eeprom space the mfr_ee_unlock, mfr_ee_erase and mfr_ee_data commands provide a method for 3rd party eeprom programming houses and end users to easily program the ltc2974 independent of any order dependencies or delays between pmbus commands. all data transfers are directly to and from the eeprom and do not affect the volatile ram space currently configuring the device. the first step is to program a master reference part with the desired configuration. mfr_ee_unlock and mfr_ee_data are then used to read back all the data in user eeprom space as sequential words. this information is stored to the master programming hex file. subsequent parts may be cloned to match the master part using mfr_ee_unlock, mfr_ee_erase and mfr_ee_data to transfer data from the master hex file. these commands operate directly on the eeprom independent of the part configurations stored in ram space. during eeprom access the part will indicate that it is busy as described below. in order to support simple programming fixtures the bulk programming features only uses pmbus word and byte com - mands. the mfr_unlock configures the appropriate access mode and resets an internal address pointer allowing a series of word commands to behave as a block read or write with the address pointer being incremented after each operation. pec use is optional and is configured by the mfr_ee_unlock operation. mfr_ee_unlock the mfr_ee_unlock command prevents accidental eeprom access in normal operation and configures the required eeprom bulk programming mode for bulk initialization, sequential writes, or reads. mfr_ee_unlock augments the protection provided by write protect. upon unlocking the part for the required operation, an internal address pointer is reset allowing a series of mfr_ee_data reads or writes to sequentially transfer data, similar to a block read or block write. the mfr_ee_unlock command can clear or set pec mode based on the desired level of error protection. an mfr_ee_unlock sequence consists of writing two unlock codes using two byte-write commands. the following table documents the allowed sequences. writing a non-supported sequence locks the part. reading mfr_ee_unlock returns the last byte written or zero if the part is locked. pmbus command description
ltc2974 42 2974fa for more information www.linear.com/ltc2974 mfr_ee_unlock data contents bit(s) symbol operation b[7:0] mfr_ee_unlock[7:0] to unlock user eeprom space for mfr_ee_erase and mfr_ee_data read or write operations with pec allowed: write 0x2b followed by 0xd4. to unlock user eeprom space for mfr_ee_erase and mfr_ee_data read or write operations with pec required: write 0x2b followed by 0xd5. to unlock user and manufacturer eeprom space for mfr_ee_data read only operations with pec allowed: write 0x2b, followed by 0x91 followed by 0xe4. to unlock user and manufacturer eeprom space for mfr_ee_data read only operations with pec required: write 0x2b, followed by 0x91 followed by 0xe5. mfr_ee_erase the mfr_ee_erase command is used to erase the entire contents of the user eeprom space and configures this space to accept new program data. writing values other than 0x2b will lock the part. reads return the last value written. mfr_ee_erase data contents bit(s) symbol operation b[7:0] mfr_ee_erase[7:0] to erase the user eeprom space and configure to accept new data: 1) use the appropriate mfr_ee_unlock sequence to configure for mfr_ee_erase commands with or without pec. 2) write 0x2b to mfr_ee_erase. the part will indicate it is busy erasing the eeprom by the mechanism detailed below. mfr_ee_data the mfr_ee_data command allows the user to transfer data directly to or from the eeprom without affecting ram space. to read the user eeprom space issue the appropriate mfr_ee_unlock command and perform mfr_ee_data reads until the eeprom has been completely read. extra reads will lock the part and return zero. the first read returns the 16-bit eeprom packing revision id that is stored in rom. the second read returns the number of 16-bit words available; this is the number of reads or writes to access all memory locations. subsequent reads return eeprom data starting with lowest address. to write to the user eeprom space issue the appropriate mfr_ee_unlock and mfr_ee_erase commands followed by successive mfr_ee_data word writes until the eeprom is full. extra writes will lock the part. the first write is to the lowest address. mfr_ee_data reads and writes must not be mixed. pmbus command description
ltc2974 43 2974fa for more information www.linear.com/ltc2974 mfr_ee_data data contents bit(s) symbol operation b[7:0] mfr_ee_data[7:0] to read user space 1) use the appropriate mfr_ee_unlock sequence to configure for mfr_ee_data commands with or without pec. 2) read mfr_ee_data[0] = packingid (mfr specific id). 3) read mfr_ee_data[1] = numberofuserwords (total number of 16-bit word available). 4) read mfr_ee_data[2] through mfr_ee_data[numberofword+1] (user eeprom data contents) to write user space 1) initialize the user memory using the sequence described for the mfr_ee_erase command. 2) use the appropriate mfr_ee_unlock sequence to configure for mfr_ee_data commands with or without pec. 3) write mfr_ee_data[0] through mfr_ee_data[numberofword-1] (user eeprom data content to be wriiten) the part will indicate it is busy erasing the eeprom by the mechanism detailed below. response when part is busy the part will indicate it is busy accessing the eeprom by the following mechanism: 1) clearing mfr_common_busyb of the mfr_common register. this byte can always be read and will never nack a byte read request even if the part is busy. 2) nacking commands other than mfr_common. mfr_ee erase and write programming time the program time per word is typically 0.17ms and will require spacing the i 2 c/smbus writes at greater than 0.17ms to guarantee the write has completed. the mfr_ee_erase command takes approximately 400ms. we recommend using mfr_common for handshaking. pmbus command description vin_on, vin_off, vin_ov_fault_limit, vin_ov_warn_limit, vin_uv_warn_limit and vin_uv_fault_limit these commands provide voltage supervising limits for the input voltage v in_sns . input voltage commands and limits command name cmd code description type paged format units eeprom default value ref page vin_on 0x35 input voltage (vin_sns) above which power conversion can be enabled. r/w word n l11 v y 10.0 0xd280 43 vin_off 0x36 input voltage (vin_sns) below which power conversion is disab led. a ll vout_en pins go off immediately or sequence off after toff_ delay (see mfr_config_track_enn). r/w word n l11 v y 9.0 0xd240 43 vin_ov_fault_limit 0x55 input overvoltage fault limit measured at vin_sns pin. r/w word n l11 v y 15.0 0xd3c0 43 vin_ov_warn_limit 0x57 input overvoltage warning limit measured at vin_sns pin. r/w word n l11 v y 14.0 0xd380 43 vin_uv_warn_limit 0x58 input undervoltage warning limit measured at vin_sns pin. r/w word n l11 v y 0 0x8000 43 vin_uv_fault_limit 0x59 input undervoltage fault limit measured at vin_sns pin. r/w word n l11 v y 0 0x8000 43
ltc2974 44 2974fa for more information www.linear.com/ltc2974 pmbus command description vout_mode this command is read only and specifies the mode and exponent for all commands with a l16 data format. see data formats on page 27. vout_mode data contents bit(s) symbol operation b[7:5] vout_mode_type reports linear mode. hard-wired to 000b. b[4:0] vout_mode_parameter linear mode exponent. 5-bit twos complement integer. hardwired to 0x13 (C13 decimal). output voltage commands and limits command name cmd code description type paged format units eeprom default value ref page vout_mode 0x20 output voltage data format and mantissa exponent (2C 13) . r byte y reg 0x13 44 vout_command 0x21 servo target. nominal dc/dc converter output voltage setpoint. r/w word y l16 v y 1.0 0x2000 45 vout_max 0x24 upper limit on the output voltage the unit can command regardless of any other commands. r/w word y l16 v y 4.0 0x8000 45 vout_margin_high 0x25 margin high dc/dc converter output voltage setting. r/w word y l16 v y 1.05 0x219a 45 vout_margin_low 0x26 margin low dc/dc converter output voltage setting. r/w word y l16 v y 0.95 0x1e66 45 vout_ov_fault_limit 0x40 output overvoltage fault limit. r/w word y l16 v y 1.1 0x2333 45 vout_ov_warn_limit 0x42 output overvoltage warning limit. r/w word y l16 v y 1.075 0x2266 45 vout_uv_warn_limit 0x43 output undervoltage warning limit. r/w word y l16 v y 0.925 0x1d9a 45 vout_uv_fault_limit 0x44 output undervoltage fault limit. used for ton_max_fault and power good de- assertion. r/w word y l16 v y 0.9 0x1ccd 45 power_good_on 0x5e output voltage at or above which a power good should be asserted. r/w word y l16 v y 0.96 0x1eb8 45 power_good_off 0x5f output voltage at or below which a power good should be de-asserted when mfr_ config_all_pwrgd_off_uses_uv is clear. r/w word y l16 v y 0.94 0x1e14 45 mfr_vout_discharge_ threshold 0xe9 coefficient used to multiply vout_ command in order to determine v out off threshold voltage. r/w word y l11 y 2.0 0xc200 45 mfr_dac 0xe0 manufacturer register that contains the code of the 10-bit dac. r/w word y reg n 0x0000 45
ltc2974 45 2974fa for more information www.linear.com/ltc2974 pmbus command description vout_command, vout_max, vout_margin_high, vout_margin_low, vout_ov_fault_limit, vout_ov_warn_limit, vout_uv_warn_limit, vout_uv_fault_limit, power_good_on and power_good_off these commands provide various servo, margining and supervising limits for a channels output voltage. mfr_vout_discharge_threshold this register contains the coefficient that multiplies vout_command in order to determine the off threshold volt - age for the associated output. if the output voltage has not decayed below mfr_vout_discharge_threshold ? vout_command prior to the channel being commanded to enter/re-enter the on state, the status_mfr_discharge bit in the status_mfr_specific register will be set and the alertb pin will be asserted low. in addition, the channel will not enter the on state until the output has decayed below its off-threshold voltage. setting this to a value greater than 1.0 effectively disables discharge_threshold checking, allowing the channel to turn back on even if it has not decayed at all. other channels can be held-off if a particular output has failed to discharge by using the bidirectional faultb n pins (refer to the mfr_faultb n _response and mfr_faultbn _propogate registers). mfr_dac this command register allows the user to directly program the 10-bit dac. manual dac writes require the channel to be in the on state,ton_rise to have expired and mfr_config_ltc2974 b[5:4] = 10b or 11b. writing mfr_ config_ltc2974 b[5:4] = 10b commands the dac to hard connect with the value in mfr_dac_direct_val. writing b[5:4] = 11b commands the dac to soft-connect. once the dac has soft-connected, mfr_dac_direct_val returns the value that allowed the dac to be connected without perturbing the power supply. mfr_dac writes are ignored when mfr_config_ltc2974 b[5:4] = 00b or 01b. mfr_dac data contents bit(s) symbol operation b[15:10] reserved read only, always returns 0. b[9:0] mfr_dac_direct_val dac code value.
ltc2974 46 2974fa for more information www.linear.com/ltc2974 iout_cal_gain the iout_cal_gain command is used to set the ratio of the voltage at the current sense pins to the sensed current. for devices using a fixed current sense resistor, it is the same value as the resistance of the resistor (units are expressed in m). iout_cal_gain is internally limited to values between 0.01m to 1,000m. the register readback value always returns what was last written and does not reflect internal limiting. calculations using iout_cal_gain are: v iout_oc_fault_limit = iout_oc_fault_limit ? iout_cal_gain ? t correction v iout_uc_fault_limit = iout_uc_fault_limit ? iout_cal_gain ? t correction where: t correction = (1 + mfr_iout_cal_gain_tc ? 1e-6 ? (read_temperature_1 + mfr_t_self_heat C 25.0)) read_iout = v iout _ snspn ? v iout _ snsmn (iout _ cal _ gain) ? t correction note: t correction is limited by hardware to a value between 0.25 and 4.0. read_temperature_2 is substituted for read_temperature_1 if the associated t sense network fails to detect a valid temperature. see read_temperature_1 for more information. pmbus command description output current commands and limits command name cmd code description type paged format units eeprom default value ref page iout_cal_gain 0x38 the nominal resistance of the current sense element in m?. r/w word y l11 m y 1.0 0xba00 46 iout_oc_fault_limit 0x46 output overcurrent fault limit. r/w word y l11 a y 10.0 0xd280 47 iout_oc_warn_limit 0x4a output overcurrent warning limit. r/w word y l11 a y 5.0 0xca80 47 iout_uc_fault_limit 0x4b output undercurrent fault limit. used to detect a reverse current and must be a negative value. r/w word y l11 a y -1.0 0xbe00 47 mfr_iout_cal_gain_tc 0xf6 temperature coefficient applied to iout_ cal_gain. r/w word y cf ppm y 0x0 47
ltc2974 47 2974fa for more information www.linear.com/ltc2974 pmbus command description iout_oc_fault_limit, iout_oc_warn_limit and iout_uc_fault_limit i out supervisor fault and warning limits. iout_oc_fault_limited is internally limited to values greater or equal to zero. the register readback value always returns what was last written and does not reflect internal limiting. iout_uc_fault_limited is internally limited to values less than zero. the register readback value always returns what was last written and does not reflect internal limiting. mfr_iout_cal_gain_tc the mfr_iout_cal_gain_tc is a paged command that sets the temperature coefficient of the iout_cal_gain register value in ppm/c. this command uses the temperature measured by the external temperature diode for the associated page. refer to iout_cal_gain for details on proper usage. mfr_iout_cal_gain_tc data contents bit(s) symbol operation b[15:0] mfr_iout_cal_gain_tc 16-bit twos complement integer representing the temperature coefficient. value = y where y = b[15:0] is a twos complement. example: mfr_iout_cal_gain_tc = 3900ppm for b[15:0] = 0x0f3c value = 3900
ltc2974 48 2974fa for more information www.linear.com/ltc2974 ot_fault_limit, ot_warn_limit, ut_warn_limit and ut_fault_limit these commands provide supervising limits for temperature as measured by the external diode. mfr_temp_1_gain and mfr_temp_1_offset the mfr_temp_1_gain command specifies the inverse of the temperature sensor ideality factor. the mfr_temp_1_ offset allows an offset to be applied to the measured temperature. calculations using these paged commands are: read_temperature_1 = t ext ? mfr_temp_1_gain C 273.15 + mfr_temp_1_offset where: t ext = measured external temperature in degrees kelvin. read_temperature_2 is substituted for read_temperature_1 if the associated t sense network fails to detect a valid temperature. under these conditions mfr_temp1_gain and mfr_temp1_offset will have no effect. see read_temperature_1 for more information. mfr_temp_1_gain data contents bit(s) symbol operation b[15:0] mfr_temp_1_gain[15:0] 16-bit integer representing inverse of temperature non-ideality factor. value = y ? 2 14 where y = b[15:0] is an unsigned integer. example: mfr_temp_1_gain = 1.0 for b[15:0] = 0x4000 value = 16384 ? 2 C14 = 1.0 pmbus command description external temperature commands and limits command name cmd code description type paged format units eeprom default value ref page ot_fault_limit 0x4f overtemperature fault limit setting for the external temperature sensor. r/w word y l11 c y 65.0 0xea08 48 ot_warn_limit 0x51 overtemperature warning limit for the external temperature sensor r/w word y l11 c y 60.0 0xe3c0 48 ut_warn_limit 0x52 undertemperature warning limit for the external temperature sensor. r/w word y l11 c y 0 0x8000 48 ut_fault_limit 0x53 undertemperature fault limit for the external temperature sensor. r/w word y l11 c y C5.0 0xcd80 48 mfr_temp_1_gain 0xf8 inverse of external diode temperature non ideality factor. one lsb = 2 C14 . r/w word y cf y 1 0x4000 48 mfr_temp_1_offset 0xf9 offset value for the external temperature. r/w word y l11 c y 0 0x8000 48 mfr_t_self_heat 0xb8 calculated temperature rise due to self-heating of output current sense device above value measured by external temperature sensor. r word y l11 c na 49 mfr_iout_cal_gain_tau_inv 0xb9 inverse of time constant for mfr_t_ self_heat changes scaled by 4 ? tconv_sense. r/w word y l11 y 0.0 0x8000 49 mfr_iout_cal_gain_theta 0xba thermal resistance from inductor core to point measured by external temperature sensor. r/w word y l11 c/w y 0.0 0x8000 49
ltc2974 49 2974fa for more information www.linear.com/ltc2974 mfr_t_self_heat, mfr_iout_cal_gain_tau_inv and mfr_iout_cal_gain_theta the ltc2974 uses an innovative (patent pending) algorithm to dynamically model the temperature rise from the external temperature sensor to the inductor core. this temperature rise is called mfr_t_self_heat and is used to calculate the final temperature correction required by iout_cal_gain. the temperature rise is a function of the power dissipated in the inductor dcr, the thermal resistance from the inductor core to the remote temperature sensor and the thermal time constant of the inductor to board system. the algorithm simplifies the placement requirements for the external temperature sensor and compensates for the significant steady state and transient temperature error from the inductor core to the primary inductor heat sink. the best way to understand the self-heating effect inside the inductor is to model the system using the circuit analogy of figure 21. the 1st order differential equation for the above model may be approximated by the following difference equation: p i C t i / is = c ?t i /?t (eq1) (when t s = 0) from which: ?t i = ?t (p i is C t i )/( is c ) (eq2) or ?t i = (p i is C t i ) ? inv (eq3) where inv = ?t/( is c ) (eq4) and ?t is the sample period of the external temperature adc. the ltc2974 implements the self-heating algorithm using eq3 and eq4 where: ?t i =?mfr_t_self_heat p i = read_iout ? (v isensep C v isensem ) t s = read_temperature_1 t i = mfr_t_self_heat + t s ?t = 4 ? t conv_sense . (one complete external temperature loop period) inv = mfr_iout_cal_gain_tau_inv is = mfr_iout_cal_gain_theta figure 21. electronic analogy for inductor temperature model i = p i p i = current representing the power dissipated by the inductor (v dcr ? read_iout where v dcr = (v isensep ? v isensm )) c = capacitance representing thermal heat capacity of the inductor (included in mfr_iout_cal_gain_tau_inv) t i = voltage representing the temperature of the inductor is = resistance representing the thermal resistance from the dcr to the remote temperature sensor (mfr_iout_cal_gain_theta) t s = voltage representing the temperature at the remote temperature sensor 2974 f21 c = c r = is v s = t s v i = t i pmbus command description
ltc2974 50 2974fa for more information www.linear.com/ltc2974 initially self heat is set to zero. after each temperature measurement self heat is updated to be the previous value of self heat incremented or decremented by ?mfr_t_self_heat. the actual value of c is not required. the important quantity is the thermal time constant inv = ( is c ). for example, if an inductor has a thermal time constant inv = 5 seconds then: mfr_iout_cal_gain_tau_inv = (4 ? t conv_sense )/5 = 4 ? 66ms/5s = 0.0528 refer to the application section for more information on calibrating is and inv . read_temperature_2 is substituted for read_temperature_1 if the associated t sense network fails to detect a valid temperature. under these conditions t s = read_temperature_2 and the self-heating correction is applied using the internal die temperature. see read_temperature_1 for more information. mfr_t_self_heat data content bit(s) symbol operation b[15:0] mfr_t_self_heat values are limited to the range 0c to 50c. mfr_iout_cal_gain_theta data content bit(s) symbol operation b[15:0] mfr_iout_cal_gain_theta values 0 set mfr_t_self_heat to zero. mfr_iout_cal_gain_tau_inv data content bit(s) symbol operation b[15:0] mfr_iout_cal_gain_tau_inv values 0 set mfr_t_self_heat to zero. values 1 set mfr_t_self_heat to mfr_iout_cal_gain_theta ? read_iout ? (v isensep C v isensem ). pmbus command description
ltc2974 51 2974fa for more information www.linear.com/ltc2974 pmbus command description ton_delay, ton_rise, ton_max_fault_limit and toff_delay these commands share the same format and provide sequencing and timer fault and warning delays in ms. ton_delay sets the amount of time in milliseconds that a channel waits following the start of an on sequence before its v out_en pin enables a dc/dc converter. this delay is counted using share_clk only. ton_rise sets the amount of time in ms that elapses after the power supply has been enabled until the ltc2974s dac soft-connects and servos the output voltage to the desired level if mfr_dac_mode = 00b. this delay is counted using share_clk only. ton_max_fault_limit is the maximum amount of time that the power supply being controlled by the ltc2974 can attempt to power up the output without reaching the vout_uv_fault_limit. if it does not, then a ton_max_fault is declared. if the output reaches vout_uv_fault_limit prior to ton_max_fault_limit, the ltc2974 unmasks the vout_uv_fault_limit threshold. (note that a value of zero means there is no limit to how long the power supply can attempt to bring up its output voltage.) this delay is counted using share_clk only. toff_delay is the amount of time that elapses after the control pin and/or operation command is de-asserted until the channel is disabled (soft-off). this delay is counted using share_clk if available, otherwise the internal oscillator is used. all of the above ton and toff delays are internally limited to 655ms, and rounded to the nearest 10s. the read value of these commands always returns what was last written and does not reflect internal limiting. mfr_restart_delay this command essentially sets the off time of a control pin initiated restart. if the control pin is toggled off for at least 10s then on, all dependent channels are disabled, held off for a time = mfr_restart_delay, then sequenced back on. control pin transitions whose off time exceeds mfr_restart_delay are not affected by this command. a value of all zeros disables this feature. this delay is counted using share_clk only. this delay is internally limited to 13.1 seconds, and rounded to the nearest 200s. the read value of this command always returns what was last written and does not reflect internal limiting. sequencing timing limits and clock sharing command name cmd code description type paged format units eeprom default value ref page ton_delay 0x60 time from control pin and/or operation command = on to v out_en pin = on. r/w word y l11 ms y 1.0 0xba00 51 ton_rise 0x61 time from when the v out_enn pin goes high until the ltc2974 optionally soft-connects its dac and begins to servo the output voltage to the desired value. r/w word y l11 ms y 10.0 0xd280 51 ton_max_fault_limit 0x62 maximum time from v out_en pin on assertion that an uv condition will be tolerated before a ton_max_fault condition results. r/w word y l11 ms y 15.0 0xd3c0 51 toff_delay 0x64 time from control pin and/or operation command = off to v out_en pin = off. r/w word y l11 ms y 1.0 0xba00 51 mfr_restart_delay 0xdc delay from actual control active edge to virtual control active edge. r/w word n l11 ms y 400 0xfb20 51
ltc2974 52 2974fa for more information www.linear.com/ltc2974 clock sharing multiple ltc pmbus devices can synchronize their clocks in an application by connecting together the open-drain share_clk input/outputs to a pull-up resistor as a wired or. in this case the fastest clock will take over and syn - chronize all other chips to its falling edge. share_clk can optionally be used to synchronize on/off dependency on v in across multiple chips by setting the mfr_config_all_vin_share_enable bit of the mfr_config_all register. when configured this way the chip will hold share_clk low when the unit is off for insufficient input voltage, and upon detecting that share_clk is held low the chip will disable all channels after a brief deglitch period. when the share_clk pin is allowed to rise, the chip will respond by beginning a start sequence. in this case the slowest vin_on detection will take over and synchronize other chips to its start sequence. pmbus command description watchdog timer and power good command name cmd code description type paged format units eeprom default value ref page mfr_pwrgd_en 0xd4 configuration that maps wdi/ resetb status and individual channel power good to the pwrgd pin. r/w word n reg y 0x0000 52 mfr_powergood_assertion_delay 0xe1 power-good output assertion delay. r/w word n l11 ms y 100 0xeb20 53 mfr_watchdog_t_first 0xe2 first watchdog timer interval. r/w word n l11 ms y 0 0x8000 53 mfr_watchdog_t 0xe3 watchdog timer interval. r/w word n l11 ms y 0 0x8000 53 mfr_pwrgd_en this command register controls the mapping of the watchdog and channel power good status to the pwrgd pin. mfr_pwrgd_en data contents bit(s) symbol operation b[15:9] reserved read only, always returns 0s. b[8] mfr_pwrgd_en_wdog watchdog. 1 = watchdog timer not-expired status is anded with pwrgd status for any similarly enabled channels to determine when the pwrgd pin gets asserted. 0 = watchdog timer does not affect the pwrgd pin. b[7:4] reserved always returns 0000b. b[3] mfr_pwrgd_en_chan3 channel 3. 1 = pwrgd status for this channel is anded with pwrgd status for any similarly enabled channels to determine when the pwrgd pin gets asserted. 0 = pwrgd status for this channel does not affect the pwrgd pin. b[2] mfr_pwrgd_en_chan2 channel 2. 1 = pwrgd status for this channel is anded with pwrgd status for any similarly enabled channels to determine when the pwrgd pin gets asserted. 0 = pwrgd status for this channel does not affect the pwrgd pin.
ltc2974 53 2974fa for more information www.linear.com/ltc2974 pmbus command description b[1] mfr_pwrgd_en_chan1 channel 1. 1 = pwrgd status for this channel is anded with pwrgd status for any similarly enabled channels to determine when the pwrgd pin gets asserted. 0 = pwrgd status for this channel does not affect the pwrgd pin. b[0] mfr_pwrgd_en_chan0 channel 0. 1 = pwrgd status for this channel is anded with pwrgd status for any similarly enabled channels to determine when the pwrgd pin gets asserted. 0 = pwrgd status for this channel does not affect the pwrgd pin. mfr_powergood_assertion_delay this command register allows the user to program the delay from when the internal power-good signal becomes valid until the power-good output is asserted. this delay is counted using share_clk if available, otherwise the internal oscillator is used. this delay is internally limited to 13.1 seconds, and rounded to the nearest 200s. the read value of this command always returns what was last written and does not reflect internal limiting. the power good de-assertion delay and threshold source is controlled by mfr_config_all_pwrgd_off_uses_uv. sys - tems that require a fast power good de-assertion should set mfr_config_all_pwrgd_off_uses_uv=1. this uses the vout_uv_fault_limit and the high speed comparator to de-assert the pwrgd pin. systems that require a separate power good off threshold should set mfr_config_all_pwrgd_off_uses_uv=0. this uses the slower adc polling loop and power_good_off to de-assert the pwrgd pin. watchdog operation a non-zero write to the mfr_watchdog_t register will reset the watchdog timer. low-to-high transitions on the wdi/resetb pin also reset the watchdog timer. if the timer expires, alertb is asserted and the pwrgd output is optionally de-asserted and then reasserted after mfr_pwrgd_assertion_delay ms. writing 0 to either the mfr_watch_dog_t or mfr_watchdog_t_first registers will disable the timer. mfr_watchdog_t_first and mfr_watchdog_t the mfr_watchdog_t_first register allows the user to program the duration of the first watchdog timer interval following assertion of the pwrgd pin, assuming the pwrgd pin reflects the status of the watchdog timer. if asser - tion of pwrgd is not conditioned by the watchdog timers status, then mfr_watchdog_t_first applies to the first timing interval after the timer is enabled. writing a value of 0ms to the mfr_watchdog_t_first register disables the watchdog timer. this delay is internally limited to 65 seconds and rounded to the nearest 1ms. the mfr_watchdog_t register allows the user to program watchdog timer intervals subsequent to the mfr_watch - dog_t_first timing interval. writing a value of 0ms to the mfr_watchdog_t register disables the watchdog timer. this delay is internally limited to 655ms and rounded to the nearest 10s. both timers operate on an internal clock independent of share_clk. the read value of both commands always returns what was last written and does not reflect internal limiting.
ltc2974 54 2974fa for more information www.linear.com/ltc2974 pmbus command description clearing latched faults latched faults are reset by toggling the control pin, using the operation command, or removing and reapplying the bias voltage to the v in_sns pin. all fault and warning conditions result in the alertb pin being asserted low and the corresponding bits being set in the status registers. the clear_faults command resets the contents of the status registers and de-asserts the alertb output. the clear_faults does not clear a faulted off state nor allow a channel to turn back on. fault responses command name cmd code description type paged format units eeprom default value ref page vout_ov_fault_response 0x41 action to be taken by the device when an output overvoltage fault is detected. r/w byte y reg y 0x80 55 vout_uv_fault_response 0x45 action to be taken by the device when an output undervoltage fault is detected. r/w byte y reg y 0x7f 55 iout_oc_fault_response 0x47 action to be taken by the device when an output overcurrent fault is detected. r/w byte y reg y 0x00 56 iout_uc_fault_response 0x4c action to be taken by the device when an output undercurrent fault is detected. r/w byte y reg y 0x00 56 ot_fault_response 0x50 action to be taken by the device when an overtemperature fault is detected on the external temperature sensor. r/w byte y reg y 0xb8 57 ut_fault_response 0x54 action to be taken by the device when an undertemperature fault is detected on the external temperature sensor. r/w byte y reg y 0xb8 57 vin_ov_fault_response 0x56 action to be taken by the device when an input overvoltage fault is detected. r/w byte n reg y 0x80 57 vin_uv_fault_response 0x5a action to be taken by the device when an input undervoltage fault is detected. r/w byte n reg y 0x00 57 ton_max_fault_response 0x63 action to be taken by the device when a ton_max_fault event is detected. r/w byte y reg y 0xb8 58 mfr_retry_delay 0xdb retry interval during fault retry mode. r/w word n l11 ms y 200 0xf320 58 mfr_retry_count 0xf7 retry count for all faulted off conditions that enable retry. r/w byte n reg y 0x00 58
ltc2974 55 2974fa for more information www.linear.com/ltc2974 pmbus command description vout_ov_fault_response and vout_uv_fault_response the fault response documented here is for voltages that are measured by the high speed supervisor. these voltages are measured over a short period of time and may require a deglitch period. note that in addition to the response described by these commands, the ltc2974 will also: ? set the appropriate bit(s) in the status_by te. ? set the appropriate bit(s) in the status_word. ? set the appropriate bit in the corresponding status_vout register , and ? notify the host by pulling the alertb pin low. vout_ov_fault_response and vout_uv_fault_response data contents bit(s) symbol operation b[7:6] vout_ov_fault_response_action, vout_uv_fault_response_action response action: 00b: the unit continues operation without interruption. 01b: the unit continues operating for the delay time specified by bits[2:0] in increments of t s_vs . see electrical characteristics table. if the fault is still present at the end of the delay time, the unit shuts down immediately or sequences off after toff_delay (see mfr_config_track_en n). after shutting down, the device responds according to the retry settings in bits [5:3]. 10b-11b: the unit shuts down immediately or sequences off after toff_delay (see mfr_config_track_enn). after shutting down, the device responds according to the retry settings in bits [5:3]. b[5:3] vout_ov_fault_response_retry, vout_uv_fault_response_retry response retry behavior: 000b: a zero value for the retry setting means that the unit does not attempt to restart. the output remains disabled until the fault is cleared. 001b-111b: the pmbus device attempts to restart the number of times specified by the global mfr_retry_ count[2:0] until it is commanded off (by the control pin or operation command or both), bias power is removed, or another fault condition causes the unit to shut down. changing the value might not take effect until the next off-then-on sequence on that channel. b[2:0] vout_ov_fault_response_delay, vout_uv_fault_response_delay this sample count determines the amount of time a unit is to ignore a fault after it is first detected. use this delay to deglitch fast faults. 000b: there is no additional deglitch delay applied to fault detection. 001b-111b: the fault is deglitched for deglitch period of b[2:0] samples at a sampling period of ts_vs (12.2s typical).
ltc2974 56 2974fa for more information www.linear.com/ltc2974 iout_oc_fault_response and iout_uc_fault_response the fault response documented here is for currents that are measured by the high speed supervisor. these currents are measured over a short period of time and may require a deglitch period. note that in addition to the response described by these commands, the ltc2974 will also: ? set the appropriate bit in the status_by te. ? set the appropriate bit in the status_word. ? set the appropriate bit in the corresponding status_iout register , and ? notify the host by pulling the alertb pin low. iout_oc_fault_resonse and iout_uc_fault_response data contents bit(s) symbol operation b[7:6] iout_oc_fault_response_action, iout_uc_fault_response_action response action: 00b and 01b: the unit continues operation without interruption. note that the current will not be limited to the value of iout_oc_fault_limit or iout_uc_fault_limit. 10b: the unit continues operating for the delay time specified by bits [2:0]. if the fault is still present at the end of the delay time, the unit shuts down immediately or sequences off after toff_delay (see mfr_config_ track_enn ). after shutting down, the device responds according to the retry settings in bits [5:3]. note that the current will not be limited to the value of iout_oc_fault_limit or iout_uc_fault_limit. 11b: the unit shuts down immediately or sequences off after toff_delay (see mfr_config_track_en n). after shutting down, the device responds according to the retry settings in bits [5:3]. b[5:3] iout_oc_fault_response_retry, iout_uc_fault_response_retry response retry behavior: 000b: a zero value for the retry setting means that the unit does not attempt to restart. the output remains disabled until the fault is cleared. 001-111b: the pmbus device attempts to restart the number of times specified by the global mfr_retry_ count[2:0] until it is commanded off (by the control pin or operation command or both), bias power is removed, or another fault condition causes the unit to shut down. changing the value might not take effect until the next off-then-on sequence on that channel. b[2:0] iout_oc_fault_response_delay, iout_uc_fault_response_delay this sample count determines the amount of time a unit is to ignore a fault after it is first detected. use this delay to deglitch fast faults. 000b: there is no additional deglitch delay applied to fault detection. 001b-111b: the fault is deglitched for the interval selected by b[2:0] as follows. b[2:0] deglitch interval 001b 100s 010b 1ms 011b 5ms 100b 10ms 101b 20ms 110b 50ms 111b 100ms pmbus command description
ltc2974 57 2974fa for more information www.linear.com/ltc2974 ot_fault_response, ut_fault_response, vin_ov_fault_response and vin_uv_fault_response the fault response documented here is for values that are measured by the adc. note that in addition to the response described by these commands, the ltc2974 will also: ? set the appropriate bit(s) in the status_by te. ? set the appropriate bit(s) in the status_word. ? set the appropriate bit in the corresponding status_vin or st atus_temperature register, and ? notify the host by pulling the alertb pin low. ot_fault_response, ut_fault_response, vin_ov_fault_response, vin_uv_fault_response data contents bit(s) symbol operation b[7:6] ot_fault_response_action, ut_fault_response_action, vin_ov_fault_response_action, vin_uv_fault_response_action response action: 00b: the unit continues operation without interruption. 01b-11b: the unit shuts down immediately or sequences off after toff_delay (see mfr_config_track_en n). after shutting down, the device responds according to the retry settings in bits [5:3]. b[5:3] ot_fault_response_retry, ut_fault_response_retry, vin_ov_fault_response_retry, vin_uv_fault_response_retry response retry behavior: 000b: a zero value for the retry setting means that the unit does not attempt to restart. the output remains disabled until the fault is cleared. 001b-111b: the pmbus device attempts to restart the number of times specified by the global mfr_retry_ count[2:0] until it is commanded off (by the control pin or operation command or both), bias power is removed, or another fault condition causes the unit to shut down. changing the value might not take effect until the next off-then-on sequence on that channel. b[2:0] ot_fault_response_delay, ut_fault_response_delay, vin_ov_fault_response_delay, vin_uv_fault_response_delay hard coded to 000b: there is no additional deglitch delay applied to fault detection. pmbus command description
ltc2974 58 2974fa for more information www.linear.com/ltc2974 pmbus command description ton_max_fault_response this command defines the ltc2974 response to a ton_max_fault. it may be used to protect against a short-circuited output at startup. after startup use vout_uv_fault_response to protect against a short-circuited output. the device also: ? sets the high_byte bit in the sta tus_byte, ? sets the vout bit in the status_word, ? sets the ton_max_fault bit in the st atus_vout register, and ? notifies the host by asserting alertb. ton_max_fault_response data contents bit(s) symbol operation b[7:6] ton_max_fault_response_action response action: 00b: the unit continues operation without interruption. 01b-11b: the unit shuts down immediately or sequences off after toff_delay (see mfr_config_track_en n). after shutting down, the device responds according to the retry settings in bits [5:3]. b[5:3] ton_max_fault_response_retry response retry behavior: 000b: a zero value for the retry setting means that the unit does not attempt to restart. the output remains disabled until the fault is cleared. 001b-111b: the pmbus device attempts to restart the number of times specified by the global mfr_retry_ count[2:0] until it is commanded off (by the control pin or operation command or both), bias power is removed, or another fault condition causes the unit to shut down. changing the value might not take effect until the next off-then-on sequence on that channel. b[2:0] ton_max_fault_response_delay hard coded to 000b: there is no additional deglitch delay applied to fault detection. mfr_retry_delay this command determines the retry interval when the ltc2974 is in retry mode in response to a fault condition. this delay is counted using share_clk only. this delay is internally limited to 13.1 seconds, and rounded to the nearest 200s. the read value of this command always returns what was last written and does not reflect internal limiting. mfr_retry_count the mfr_retry_count is a global command that sets the number of retries attempted when any channel faults off with its fault response retry field set to a non zero value. in the event of multiple or recurring retry faults on the same channel the total number of retries equals mfr_retry_ count. if a channel has not been faulted off for 6 seconds, its retry counter is cleared. toggling a channels control pin off then on or issuing operation off then on commands will synchronously clear the retry count. mfr_retry_count data contents bit(s) symbol operation b[7:3] reserved always returns zero. b[2:0] mfr_retry_count [2:0] 0: no retries: 1-6: number of retries. 7: infinite retries. changing the value might not take effect until the next off-then-on sequence on that channel.
ltc2974 59 2974fa for more information www.linear.com/ltc2974 mfr_faultb0_propagate and mfr_faultb1_propagate these manufacturer specific commands enable channels that have faulted off to propagate that state to the appro - priate fault pin. mfr_faultb0_propagate allows any channels faulted off state to propagate to the faultb0 pin. mfr_faultb1_propagate allows any channels faulted off state to propagate to the faultb1 pin. note that pulling a fault pin low will have no effect for channels that have mfr_faultbn_response set to 0. the channel continues operation without interruption. this fault response is called ignore (0x0) in ltpowerplay. mfr_fault0_propagate data contents bit(s) symbol operation b[7:1] reserved dont care. always returns 0. b[0] mfr_faultb0_propagate enable fault propagation. 0: channels faulted off state does not assert faultb0 low. 1 :channels faulted off state asserts faultb0 low. mfr_fault1_propagate data contents bit(s) symbol operation b[7:1] reserved dont care. always returns 0. b[0] mfr_faultb1_propagate enable fault propagation. 0: channels faulted off state does not assert faultb1 low. 1: channels faulted off state asserts faultb1 low. pmbus command description shared external faults command name cmd code description type paged format units eeprom default value ref page mfr_faultb0_propagate 0xd2 configuration that determines if a channels faulted off state is propagated to the faultb0 pin. r/w byte y reg y 0x00 59 mfr_faultb1_propagate 0xd3 configuration that determines if a channels faulted off state is propagated to the faultb1 pin. r/w byte y reg y 0x00 59 mfr_faultb0_response 0xd5 action to be taken by the device when the faultb0 pin is asserted low. r/w byte n reg y 0x00 60 mfr_faultb1_response 0xd6 action to be taken by the device when the faultb1 pin is asserted low. r/w byte n reg y 0x00 60
ltc2974 60 2974fa for more information www.linear.com/ltc2974 mfr_faultb0_response and mfr_faultb1_response these manufacturer specific commands share the same format and specify the response to assertions of the faultb pins. mfr_faultb0_response determines which channels shut off when the faultb0 pin is asserted low and mfr_faultb1_response determines which channels shut off when the faultb1 pin is asserted low.when a chan - nel shuts off in response to a faultb n pin, the alertb pin is asserted low and the appropriate bit is set in the sta - tus_mfr_specific register. for a graphical explanation, see the switches on the left hand side of figure 28: channel fault management block diagram. faults will not propagate for channels that have mfr_faultb n _response set to 0: the channel continues operation without interruption. note that this fault response is called no action in ltpowerplay. mfr_faultb0_response and mfr_faultb1_response data contents bit(s) symbol operation b[7:4] reserved read only, always returns 0000b. b[3] mfr_faultb0_response_chan3, mfr_faultb1_response_chan3 channel 3 response. 0: the channel continues operation without interruption 1: the channel shuts down if the corresponding faultb pin is still asserted after 10s. when the faultb pin subsequently de-asserts, the channel turns back on, honoring ton_delay and ton_rise settings. b[2] mfr_faultb0_response_chan2, mfr_faultb1_response_chan2 channel 2 response. 0: the channel continues operation without interruption 1: the channel shuts down if the corresponding faultb pin is still asserted after 10s. when the faultb pin subsequently de-asserts, the channel turns back on, honoring ton_delay and ton_rise settings. b[1] mfr_faultb0_response_chan1, mfr_faultb1_response_chan1 channel 1 response. 0: the channel continues operation without interruption 1: the channel shuts down if the corresponding faultb pin is still asserted after 10s. when the faultb pin subsequently de-asserts, the channel turns back on, honoring ton_delay and ton_rise settings. b[0] mfr_faultb0_response_chan0, mfr_faultb1_response_chan0 channel 0 response. 0: the channel continues operation without interruption 1: the channel shuts down if the corresponding faultb pin is still asserted after 10s. when the faultb pin subsequently de-asserts, the channel turns back on, honoring ton_delay and ton_rise settings. pmbus command description
ltc2974 61 2974fa for more information www.linear.com/ltc2974 clear_faults the clear_faults command is used to clear status bits that have been set. this command clears all fault and warn - ing bits in all unpaged status registers, and paged status registers selected by the current page setting. at the same time, the device negates (clears, releases) its contribution to alertb. the clear_faults command does not cause a unit that has latched off for a fault condition to restart. see clearing latched faults for more information. if the fault is present after the fault is cleared, the fault status bit shall be set again and the host notified by the usual means. note: this command responds to the global page command. (page=0xff) status_byte the status_byte command returns the summary of the most critical faults or warnings which have occurred, as shown in the following table. status_byte is a subset of status_word and duplicates the same information. status_byte data contents bit(s) symbol operation b[7] status_byte_busy same as status_word_busy. b[6] status_byte_off same as status_word_off. b[5] status_byte_vout_ov same as status_word_vout_ov. b[4] status_byte_iout_oc same as status_word_iout_oc. b[3] status_byte_vin_uv same as status_word_vin_uv. b[2] status_byte_temp same as status_word_temp. b[1] status_byte_cml same as status_word_cml. b[0] status_byte_high_byte same as status_word_high_byte. pmbus command description fault warning and status command name cmd code description type paged format units eeprom default value ref page clear_faults 0x03 clear any fault bits that have been set. send byte y na 61 status_byte 0x78 one byte summary of the units fault condition. r byte y reg na 61 status_word 0x79 two byte summary of the units fault condition. r word y reg na 62 status_vout 0x7a output voltage fault and warning status. r byte y reg na 62 status_iout 0x7b output current fault and warning status. r byte y reg na 63 status_input 0x7c input supply fault and warning status. r byte n reg na 63 status_temperature 0x7d external temperature fault and warning status for read_temperature_1. r byte y reg na 63 status_cml 0x7e communication and memory fault and warning status. r byte n reg na 64 status_mfr_specific 0x80 manufacturer specific fault and state information. r byte y reg na 64 mfr_pads 0xe5 current state of selected digital i/o pads. r/w word n reg na 65 mfr_common 0xef manufacturer status bits that are common across multiple ltc chips. r byte n reg na 65
ltc2974 62 2974fa for more information www.linear.com/ltc2974 status_word the status_word command returns two bytes of information with a summary of the units fault condition. based on the information in these bytes, the host can get more information by reading the appropriate detailed status register. the low byte of the status_word is the same register as the status_byte command. status_word data contents bit(s) symbol operation b[15] status_word_vout an output voltage fault or warning has occurred. see status_vout. b[14] status_word_iout an output current fault or warning has occurred. see status_iout. b[13] status_word_input an input voltage fault or warning has occurred. see status_input. b[12] status_word_mfr a manufacturer specific fault has occurred. see status_mfr._specific. b[11] status_word_power_not_good the pwrgd pin, if enabled, is negated. power is not good. b[10] status_word_fans not supported. always returns 0. b[9] status_word_other not supported. always returns 0. b[8] status_word_unknown not supported. always returns 0. b[7] status_word_busy device busy when pmbus command received. see operation: processing commands. b[6] status_word_off this bit is asserted if the unit is not providing power to the output, regardless of the reason, including simply not being enabled. the off-bit is clear if unit is allowed to provide power to the output. b[5] status_word_vout_ov an output overvoltage fault has occurred. b[4] status_word_iout_oc an output overcurrent fault has occurred. b[3] status_word_vin_uv a v in undervoltage fault has occurred. b[2] status_word_temp a temperature fault or warning has occurred. see status_temperature. b[1] status_word_cml a communication, memory or logic fault has occurred. see status_cml. b[0] status_word_high_byte a fault/warning not listed in b[7:1] has occurred. status_vout the status_vout command returns the summary of the output voltage faults or warnings which have occurred, as shown in the following table: status_vout data contents bit(s) symbol operation b[7] status_vout_ov_fault overvoltage fault. b[6] status_vout_ov_warn overvoltage warning. b[5] status_vout_uv_warn undervoltage warning b[4] status_vout_uv_fault undervoltage fault. b[3] status_vout_max_fault vout_max fault. an attempt has been made to set the output voltage to a value higher than allowed by the vout_max command. after being cleared, status_vout_max_fault will not report additional faults until a channel state transition (off-then-on) has been performed or a valid output voltage, lower than allowed by vout_max, has been set. b[2] status_vout_ton_max_fault ton_max_fault sequencing fault. b[1] status_vout_toff_max_warn not supported. always returns 0. b[0] status_vout_tracking_error not supported. always returns 0. pmbus command description
ltc2974 63 2974fa for more information www.linear.com/ltc2974 status_iout the status_iout command returns the summary of the output current faults or warnings which have occurred, as shown in the following table: status_iout data contents bit(s) symbol operation b[7] status_iout_oc_fault overcurrent fault. b[6] status_iout_oc_uv_fault not supported. always returns 0. b[5] status_iout_oc_warn overcurrent warning b[4] status_iout_uc_fault undercurrent fault. b[3] status_iout_curr_share_fault not supported. always returns 0. b[2] status_pout_power_limiting not supported. always returns 0. b[1] status_pout_overpower_fault not supported. always returns 0. b[0] status_pout_overpower_warn not supported. always returns 0. status_input the status_input command returns the summary of the v in faults or warnings which have occurred, as shown in the following table: status_input data contents bit(s) symbol operation b[7] status_input_ov_fault v in overvoltage fault b[6] status_input_ov_warn v in overvoltage warning b[5] status_input_uv_warn v in undervoltage warning b[4] status_input_uv_fault v in undervoltage fault b[3] status_input_off unit is off for insufficient input voltage. b[2] iin overcurrent fault not supported. always returns 0. b[1] iin overcurrent warn not supported. always returns 0. b[0] pin overpower warn not supported. always returns 0. status_temperature the status_temperature command returns the summary of the temperature faults or warnings which have oc - curred, as shown in the following table. note that this information is paged and refers to the temperature of the as - sociated external diode. status_temperature data contents bit(s) symbol operation b[7] status_temperature_ot_fault overtemperature fault. b[6] status_temperature_ot_warn overtemperature warning. b[5] status_temperature_ut_warn undertemperature warning. b[4] status_temperature_ut_fault undertemperature fault. b[3] reserved reserved. always returns 0. b[2] reserved reserved. always returns 0. b[1] reserved reserved. always returns 0. b[0] reserved reserved. always returns 0. pmbus command description
ltc2974 64 2974fa for more information www.linear.com/ltc2974 status_cml the status_cml command returns the summary of the communication, memory and logic faults or warnings which have occurred, as shown in the following table: status_cml data contents bit(s) symbol operation b[7] status_cml_cmd_fault 1 = an illegal or unsupported command fault has occurred. 0 = no fault has occurred. b[6] status_cml_data_fault 1 = illegal or unsupported data received. 0 = no fault has occurred. b[5] status_cml_pec_fault 1 = a packet error check fault has occurred. note: pec checking is always active in the ltc2974. any extra byte received before a stop will set status_cml_pec_fault unless the extra byte is a matching pec byte. 0 = no fault has occurred. b[4] status_cml_memory_fault 1 = a fault has occurred in the eeprom. 0 = no fault has occurred. b[3] status_cml_processor_fault not supported, always returns 0. b[2] reserved reserved, always returns 0. b[1] status_cml_pmbus_fault 1 = a communication fault other than ones listed in this table has occurred. this is a catch all category for illegally formed i 2 c/smbus commands (example: an address byte with read =1 received immediately after a start). 0 = no fault has occurred. b[0] status_cml_unknown_fault not supported, always returns 0. status_mfr_specific the status_mfr_specific command returns manufacturer specific status flags. bits marked channel = all are not paged. bits marked sticky = yes stay set until a clear_faults is issued or the channel is commanded on by the user. bits marked alert = yes pull alertb low when the bit is set. bits marked off = yes indicate that the event can be configured elsewhere to turn the channel off. status_mfr_specific data contents bit(s) symbol operation channel sticky alert off b[7] status_mfr_discharge 1 = a v out discharge fault occurred while attempting to enter the on state. 0 = no v out discharge fault has occurred. current page yes yes yes b[6] status_mfr_fault1_in this channel attempted to turn on while the faultb1 pin was asserted low, or this channel has shut down at least once in response to a faultb1 pin asserting low since the last control pin toggle, operation command on/off cycle or clear_faults command. if mfr_track_en_chann is set, status_mfr_fault1_in may also be set for the channel causing the fault. current page yes yes yes b[5] status_mfr_fault0_in this channel attempted to turn on while the faultb0 pin was asserted low, or this channel has shut down at least once in response to a faultb0 pin asserting low since the last control pin toggle, operation command on/off cycle or clear_faults command. if mfr_track_en_chann is set, status_mfr_fault0_in may also be set for the channel causing the fault. current page yes yes yes b[4] status_mfr_servo_target_reached servo target has been reached. current page no no no b[3] status_mfr_dac_connected dac is connected and driving v dac pin. current page no no no pmbus command description
ltc2974 65 2974fa for more information www.linear.com/ltc2974 b[2] status_mfr_dac_saturated a previous servo operation terminated with maximum or minimum dac value. current page yes no no b[1] status_mfr_auxfaultb_faulted_off auxfaultb has been de-asserted due to a v out or i out fault. all no no no b[0] status_mfr_watchdog_fault 1 = a watchdog fault has occurred. 0 = no watchdog fault has occurred. all yes yes no mfr_pads the mfr_pads command provides read-only access of digital pads (pins). the input values are before any deglitch - ing logic. mfr_pads data contents bit(s) symbol operation b[15] mfr_pads_pwrgd_drive 0 = pwrgd pad is being driven low by this chip. 1 = pwrgd pad is not being driven low by this chip. b[14] mfr_pads_alertb_drive 0 = alertb pad is being driven low by this chip. 1 = alertb pad is not being driven low by this chip. b[13:12] mfr_pads_faultb_drive[1:0] bit[1] used for faultb0 pad, bit[0] used for faultb1 pad as follows: 0 = faultb pad is being driven low by this chip. 1 = faultb pad is not being driven low by this chip. b[11:10] reserved[1:0] always returns 00b. b[9:8] mfr_pads_asel1[1:0] 11: logic high detected on asel1 input pad. 10: asel1 input pad is floating. 01: reserved. 00: logic low detected on asel1 input pad. b[7:6] mfr_pads_asel0[1:0] 11: logic high detected on asel0 input pad. 10: asel0 input pad is floating. 01: reserved. 00: logic low detected on asel0 input pad. b[5] mfr_pads_control1 1: logic high detected on control1 pad. 0: logic low detected on control1 pad. b[4] mfr_pads_control0 1: logic high detected on control0 pad. 0: logic low detected on control0 pad. b[3:2] mfr_pads_faultb[1:0] bit[1] used for faultb0 pad, bit[0] used for faultb1 pad as follows: 1: logic high detected on faultb pad. 0: logic low detected on faultb pad. b[1] mfr_pads_control2 1: logic high detected on control2 pad. 0: logic low detected on control2 pad. b[0] mfr_pads_control3 1: logic high detected on control3 pad. 0: logic low detected on control3 pad. mfr_common this command returns status information for the alert, device busy, share-clock pin (share_clk) and the write-protect pin (wp). pmbus command description
ltc2974 66 2974fa for more information www.linear.com/ltc2974 this is the only command that may still be read when the ltc2974 is busy processing an eeprom or other command. it may be polled by the host to determine when the ltc2974 is available to process a pmbus command. a busy device will always acknowledge its address but will nack the command byte and set status_byte_busy and status_word_busy when it receives a command that it cannot immediately process. alertb will not be asserted low in this case. mfr_common data contents bit(s) symbol operation b[7] mfr_common_alertb returns alert status. 1: alertb is de-asserted high. 0: alertb is asserted low. b[6] mfr_common_busyb returns device busy status. 1: the device is available to process pmbus commands. 0: the device is busy and will nack pmbus commands. b[5:2] reserved read only, always returns 1s. b[1] mfr_common_share_clk returns the status of the share-clock pin. 1: share-clock pin is being held low. 0: share-clock pin is active. b[0] mfr_common_write_protect returns the status of the write-protect pin. 1: write-protect pin is high. 0: write-protect pin is low. pmbus command description telemetry command name cmd code description type paged format units eeprom default value ref page read_vin 0x88 input supply voltage. r word n l11 v na 67 read_vout 0x8b dc/dc converter output voltage. r word y l16 v na 67 read_iout 0x8c dc/dc converter output current. r word y l11 a na 67 read_temperature_1 0x8d external diode junction temperature. this is the value used for all temperature related processing, including iout_cal_gain. r word y l11 c na 67 read_temperature_2 0x8e internal junction temperature. r word n l11 c na 67 read_pout 0x96 dc/dc converter output power. r word y l11 w na 67 mfr_read_iout 0xbb alternate data format for read_iout. one lsb = 2.5ma. r word y cf 2.5ma na 67 mfr_iout_sense_voltage 0xfa absolute value of visensep C visensem. one lsb = 3.05v. r word y cf 3.05v na 68 mfr_vin_peak 0xde maximum measured value of read_vin. r word n l11 v na 69 mfr_vout_peak 0xdd maximum measured value of read_vout. r word y l16 v na 69 mfr_iout_peak 0xd7 maximum measured value of read_iout. r word y l11 a na 69 mfr_temperature_1_peak 0xdf maximum measured value of read_ temperature_1. r word y l11 c na 69 mfr_vin_min 0xfc minimum measured value of read_vin. r word n l11 v na 69 mfr_vout_min 0xfb minimum measured value of read_vout. r word y l16 v na 69 mfr_iout_min 0xd8 minimum measured value of read_iout. r word y l11 a na 69 mfr_temperature_1_min 0xfd minimum measured value of read_ temperature_1. r word y l11 c na 69
ltc2974 67 2974fa for more information www.linear.com/ltc2974 read_vin this command returns the most recent adc measured value of the input voltage at the v in_sns pin. read_vout this command returns the most recent adc measured value of the channels output voltage. read_iout this command returns the most recent adc measured value of the channels output current. read_temperature_1 this command returns the most recent measured value of the external diode temperature in c. this value is used for all temperature related operations and calculations. this command is paged. read_temperature_2 is substituted for read_temperature_1 if the associated t sense network fails to detect a valid temperature. the t sense network will fail to detect a valid temperature under the following conditions: the t sense pin is shorted to a constant voltage. the sense diode has an ideality factor greater than n_ts max. floating the t sense pin is not recommended and may return unpredictable temperature values. read_temperature_2 this command returns the most recent adc measured value of junction temperature in c as determined by the ltc2974s internal temperature sensor. this register is for information purposes and does not generate any faults, warnings, or affect any other registers or internal calculations unless it is used as read_temperature_1. this command is not paged. read_temperature_2 is substituted for read_temperature_1 if a channels t sense network fails to detect a valid temperature. read_pout this command returns the most recent adc measured value of the channels output power in watts. mfr_read_iout this command returns the most recent adc measured value of the channels output current, using a custom format that provides better numeric representation granularity than the read_iout command for currents whose absolute value is between 2a and 82a. pmbus command description
ltc2974 68 2974fa for more information www.linear.com/ltc2974 mfr_read_iout data contents bit(s) symbol operation b[15:0] mfr_read_iout[15:0] channel output current expressed in custom format for improved resolution at high currents. value = y ? 2.5 where y = b[15:0] is a signed twos-complement number. example: mfr_read_iout = 5ma for b[15:0] = 0x0002 value = 2 ? 2.5 = 5ma the granularity of the returned value is always 2.5ma, and the return value is limited to 81.92a. use the read_iout command for larger currents. note that the accuracy of the returned value is always limited by the adc characteristics listed in the electrical characteristics section. comparison of granularity due to numeric format current range read_iout granularity mfr_read_iout granularity 31.25ma i out < 62.5ma 61a 2.5ma 62.5ma i out < 125ma 122a 2.5ma 125ma i out < 250ma 244a 2.5ma 250ma i out < 500ma 488a 2.5ma 0.5a i out < 1a 977a 2.5ma 1a i out < 2a 1.95ma 2.5ma 2a i out < 4a 3.9ma 2.5ma 4a i out < 8a 7.8ma 2.5ma 8a i out < 16a 15.6ma 2.5ma 16a i out < 32a 31.3ma 2.5ma 32a i out < 64a 62.5ma 2.5ma 64a i out < 82a 125ma 2.5ma 82a i out < 128a 125ma saturated 128a i out < 256a 250ma saturated mfr_iout_sense_voltage this command returns the absolute value of the voltage measured between i sensepn and i sensemn during the last read_iout adc conversion without any temperature correction. mfr_iout_sense_voltage data contents bit(s) symbol operation b[15:0] mfr_iout_sense_voltage absolute value of raw voltage conversion measured between i sensepn and i sensemn . value = y ? 0.025 ? 2 C13 where y = b[15:0] is an unsigned integer. example: mfr_iout_sense_voltage = 1.544mv for b[15:0] = 0x1fa=506 value = 506 ? 0.025 ? 2 C13 = 1.544mv pmbus command description
ltc2974 69 2974fa for more information www.linear.com/ltc2974 mfr_vin_peak this command returns the maximum adc measured value of the input voltage. this register is reset to 0x7c00 (C2 25 ) when the ltc2974 emerges from power-on reset or when a clear_faults command is executed. mfr_vout_peak this command returns the maximum adc measured value of the channels output voltage. this register is reset to 0xf800 (0.0) when the ltc2974 emerges from power-on reset or when a clear_faults command is executed. mfr_iout_peak this commands returns the maximum adc measured value of the channels output current. this register is reset to 0x7c00 (C2 25 ) when the ltc2974 emerges from power-on reset or when a clear_faults command is executed. mfr_temperature_1_peak this command returns the maximum measured value of the external diode temperature in c. this register is reset to 0x7c00 (C2 25 ) when the ltc2974 emerges from power-on reset or when a clear_faults command is executed. mfr_vin_min this command returns the minimum adc measured value of the input voltage. this register is reset to 0x7bff (ap - proximately 2 25 ) when the ltc2974 emerges from power-on reset or when a clear_faults command is executed. mfr_vout_min this command returns the minimum adc measured value of the channels output voltage. this register is reset to 0xffff (7.9999) when the ltc2974 emerges from power-on reset or when a clear_faults command is executed. updates are disabled when margin low (ignore faults and warnings) is enabled. mfr_iout_min this command returns the minimum adc measured values of the channels output current. this register is reset to 0x7bff (approximately 2 25 ) when the ltc2974 emerges from power-on reset or when a clear_faults command is executed. mfr_temperature_1_min this command returns the minimum measured value of the external diode temperature in c. this register is reset to 0x7bff (approximately 2 25 ) when the ltc2974 emerges from power-on reset or when a clear_faults command is executed. pmbus command description
ltc2974 70 2974fa for more information www.linear.com/ltc2974 pmbus command description fault log operation a conceptual diagram of the fault log is shown in figure 22. the fault log provides black box capability for the ltc2974. during normal operation the contents of the status registers, the output voltage/current/temperature readings, the input voltage readings, as well as peak and min values of these quantities, are stored in a continuously updated buffer in ram. you can think of the operation as being similar to a strip chart recorder. when a fault occurs, the contents are written into eeprom for non volatile storage. the eeprom fault log is then locked. the part can be powered down with the fault log available for reading at a later time. figure 22: fault logging 2974 f22 adc readings continuously fill buffer time of fault transfer to eeprom and lock after fault read from eeprom and lock buffer ram 255 bytes eeprom 255 bytes 8 . . . . . . mfr_fault_log_store this command allows the user to transfer data from the ram buffer to eeprom. mfr_fault_log_restore this command allows the user to transfer a copy of the fault-log data from the eeprom to the ram buffer. after a restore the ram buffer is locked until a successful mfr_fault_log read. fault logging command name cmd code description type paged format units eeprom default value ref page mfr_fault_log_store 0xea command a transfer of the fault log from ram to eeprom. send byte n na 70 mfr_fault_log_restore 0xeb command a transfer of the fault log previously stored in eeprom back to ram. send byte n na 70 mfr_fault_log_clear 0xec initialize the eeprom block reserved for fault logging and clear any previous fault logging locks. send byte n na 71 mfr_fault_log_status 0xed fault logging status. r byte n reg y na 71 mfr_fault_log 0xee fault log data bytes. this sequentially retrieved data is used to assemble a complete fault log. r block n reg y na 71
ltc2974 71 2974fa for more information www.linear.com/ltc2974 pmbus command description mfr_fault_log_clear this command initializes the eeprom block reserved for fault logging. any previous fault log stored in eeprom will be erased by this operation and logging of the fault log ram to eeprom will be enabled. make sure that mfr_fault_ log_status_ram = 0 before issuing the mfr_fault_log_clear command. mfr_fault_log_status this register is used to manage fault log events. the mfr_fault_log_status_eeprom bit is set after a mfr_fault_log_ store command or a faulted-off event triggers a transfer of the fault log from ram to eeprom. this bit is cleared by a mfr_fault_log_clear command. mfr_fault_log_status_ram is set after a mfr_fault_ log_restore to indicate that the data in the ram has been restored from eeprom and not yet read using a mfr_fault_log command. this bit is cleared only by a successful execution of an mfr_fault_log command. mfr_fault_log_status data contents bit(s) symbol operation b[7:2] reserved read only, always returns 0s. b[1] mfr_fault_log_status_ram fault log ram status: 0: the fault log ram allows updates. 1: the fault log ram is locked until the next mfr_fault_log read. b[0] mfr_fault_log_status_eeprom fault log eeprom status: 0: the transfer of the fault log ram to the eeprom is enabled. 1: the transfer of the fault log ram to the eeprom is inhibited. mfr_fault_log read only. this 2040-bit (255 byte) data block contains a copy of the ram buffer fault log. the ram buffer is continu - ously updated after each adc conversion as long as mfr_fault_log_status_ram is clear. with mfr_config_all_fault_log_enable = 1 and mfr_fault_log_status_eeprom = 0, the ram buffer is transferred to ee - prom whenever an ltc2974 fault causes a channel to latch off or a mfr_fault_log_store command is received. this transfer is delayed until the adc has updated its read values for all channels when mfr_config_all_fast_fault_log is clear, otherwise it happens within 24ms. this optional delay can be used to ensure that the slower adc monitored values are all updated for the case where a fast supervisor detected fault initiates the transfer to eeprom. mfr_fault_log_status_eeprom is set high after the ram buffer is transferred to eeprom and not cleared until a mfr_fault_log_clear is received, even if the ltc2974 is reset or powered down. fault log eeprom transfers are not initiated as a result of status_mfr_discharge events. during a mfr_fault_log read, data is returned one byte at a time as defined in table 2. the fault log data is parti - tioned into two sections. the first section is referred to as the preamble and contains the position_last pointer, time information and peak and min values. the second section contains a chronological record of telemetry and requires position_last for proper interpretation. the fault log stores approximately 300ms of telemetry. to prevent timeouts during block reads, it is recommended that mfr_config_all_longer_pmbus_timeout be set to 1.
ltc2974 72 2974fa for more information www.linear.com/ltc2974 table 2. data block contents d ata byte* description position_last[7:0] 0 position of fault log pointer when fault occurred. sharedtime[7:0] 1 41-bit share-clock counter value when fault occurred. counter lsb is in 200s increments. sharedtime[15:8] 2 sharedtime[23:16] 3 sharedtime[31:24] 4 sharedtime[39:32] 5 sharedtime[40] 6 mfr_vout_peak0[7:0] 7 mfr_vout_peak0[15:8] 8 mfr_vout_min0[7:0] 9 mfr_vout_min0[15:8] 10 mfr_temperature_peak0[7:0] 11 mfr_temperature_peak0[15:8] 12 mfr_temperature_min0[7:0] 13 mfr_temperature_min0[15:8] 14 mfr_iout_peak0[7:0] 15 mfr_iout_peak0[15:8] 16 mfr_iout_min0[7:0] 17 mfr_iout_min0[15:8] 18 mfr_vin_peak[7:0] 19 mfr_vin_peak[15:8] 20 mfr_vin_min[7:0] 21 mfr_vin_min[15:8] 22 mfr_vout_peak1[7:0] 23 mfr_vout_peak1[15:8] 24 mfr_vout_min1[7:0] 25 mfr_vout_min1[15:8] 26 mfr_temperature_peak1[7:0] 27 mfr_temperature_peak1[15:8] 28 mfr_temperature_min1[7:0] 29 mfr_temperature_min1[15:8] 30 mfr_iout_peak1[7:0] 31 mfr_iout_peak1[15:8] 32 mfr_iout_min1[7:0] 33 mfr_iout_min1[15:8] 34 mfr_vout_peak2[7:0] 35 mfr_vout_peak2[15:8] 36 mfr_vout_min2[7:0] 37 mfr_vout_min2[15:8] 38 pmbus command description table 2. data block contents d ata byte* description mfr_temperature_peak2[7:0] 39 mfr_temperature_peak2[15:8] 40 mfr_temperature_min2[7:0] 41 mfr_temperature_min2[15:8] 42 mfr_iout_peak2[7:0] 43 mfr_iout_peak2[15:8] 44 mfr_iout_min2[7:0] 45 mfr_iout_min2[15:8] 46 mfr_vout_peak3[7:0] 47 mfr_vout_peak3[15:8] 48 mfr_vout_min3[7:0] 49 mfr_vout_min3[15:8] 50 mfr_temperature_peak3[7:0] 51 mfr_temperature_peak3[15:8] 52 mfr_temperature_min3[7:0] 53 mfr_temperature_min3[15:8] 54 mfr_iout_peak3[7:0] 55 mfr_iout_peak3[15:8] 56 mfr_iout_min3[7:0] 57 mfr_iout_min3[15:8] 58 status_vout0[7:0] 59 status_iout0[7:0] 60 status_mfr_specific0[7:0] 61 status_vout1[7:0] 62 status_iout1[7:0] 63 status_mfr_specific1[7:0] 64 status_vout2[7:0] 65 status_iout2[7:0] 66 status_mfr_specific2[7:0] 67 status_vout3[7:0] 68 status_iout3[7:0] 69 status_mfr_specific3[7:0] 70 71 bytes for preamble fault_log [position_last] 71 fault_log [position_last-1] 72 . . . fault_log [position_last-170] 237 reserved 238- 254
ltc2974 73 2974fa for more information www.linear.com/ltc2974 pmbus command description table 2. data block contents d ata byte* description number of loops: (238 C 71)/54 = 3.1 *note that pmbus data byte numbers start at 1 rather than 0. see figure 13 block read. the data returned between bytes 71 and 237 of the previous table is interpreted using position_last and the following table. the key to identifying the data located in byte 71 is to locate the data corresponding to position = position_last in the next table. subsequent bytes are identified by decrementing the value of position. for example: if position_last = 8 then the first data returned in a block read is status_temperature of page 0 followed by read_temperature_1[15:8] of page 0 followed by read_temperature_1[7:0] of page 0 and so on. see table 3. table 3. interpreting cyclical loop data position d ata 0 read_temperature_2[7:0] 1 read_temperature_2[15:8] 2 read_vout0[7:0] 3 read_vout0[15:8] 4 status_vout0[7:0] 5 status_mfr_specific0[7:0] 6 read_temperature_1_0[7:0] 7 read_temperature_1_0[15:8] 8 status_temperature0[7:0] 9 status_iout0[7:0] 10 read_iout0[7:0] 11 read_iout0[15:8] 12 read_pout0[7:0] 13 read_pout0[15:8] 14 read_vin[7:0] 15 read_vin[15:8] 16 status_input[7:0] 17 0x0 18 read_vout1[7:0] position d ata 19 read_vout1[15:8] 20 status_vout1[7:0] 21 status_mfr_specific1[7:0] 22 read_temperature_1_1[7:0] 23 read_temperature_1_1[15:8] 24 status_temperature1[7:0] 25 status_iout1[7:0] 26 read_iout1[7:0] 27 read_iout1[15:8] 28 read_pout1[7:0] 29 read_pout1[15:8] 30 read_vout2[7:0] 31 read_vout2[15:8] 32 status_vout2[7:0] 33 status_mfr_specific2[7:0] 34 read_temperature_1_2[7:0] 35 read_temperature_1_2[15:8] 36 status_temperature2[7:0] 37 status_iout2[7:0] 38 read_iout2[7:0] 39 read_iout2[15:8] 40 read_pout2[7:0] 41 read_pout2[15:8] 42 read_vout3[7:0] 43 read_vout3[15:8] 44 status_vout3[7:0] 45 status_mfr_specific3[7:0] 46 read_temperature_1_3[7:0] 47 read_temperature_1_3[15:8] 48 status_temperature3[7:0] 49 status_iout3[7:0] 50 read_iout3[7:0] 51 read_iout3[15:8] 52 read_pout3[7:0] 53 read_pout3[15:8] total bytes = 54
ltc2974 74 2974fa for more information www.linear.com/ltc2974 data block contents preamble information byte number decimal byte number hex d ata description 0 00 position_last[7:0] = 13 position of fault- log pointer when fault occurred. 1 01 sharedtime[7:0] 41-bit share- clock counter value when fault occurred. counter lsb is in 200s increments. 2 02 sharedtime[15:8] 3 03 sharedtime[23:16] 4 04 sharedtime[31:24] 5 05 sharedtime[39:32] 6 06 sharedtime[40] 7 07 mfr_vout_peak0[7:0] 8 08 mfr_vout_peak0[15:8] 9 09 mfr_vout_min0[7:0] 10 0a mfr_vout_min0[15:8] 11 0b mfr_temperature_ peak0[7:0] 12 0c mfr_temperature_ peak0[15:8] 13 0d mfr_temperature_ min0[7:0] 14 0e mfr_temperature_ min0[15:8] 15 0f mfr_iout_peak0[7:0] 16 10 mfr_iout_peak0[15:8] 17 11 mfr_iout_min0[7:0] 18 12 mfr_iout_min0[15:8] 19 13 mfr_vin_peak_[7:0] 20 14 mfr_vin_peak_[15:8] 21 15 mfr_vin_min_[7:0] 22 16 mfr_vin_min_[15:8] 23 17 mfr_vout_peak1[7:0] 24 18 mfr_vout_peak1[15:8] 25 19 mfr_vout_min1[7:0] 26 1a mfr_vout_min1[15:8] 27 1b mfr_temperature_ peak1[7:0] mfr_fault_log read example the following table fully decodes a sample fault log read with position_last = 13 to help clarify the cyclical nature of the operation. pmbus command description preamble information byte number decimal byte number hex d ata description 28 1c mfr_temperature_ peak1[15:8] 29 1d mfr_temperature_ min1[7:0] 30 1e mfr_temperature_ min1[15:8] 31 1f mfr_iout_peak1[7:0] 32 20 mfr_iout_peak1[15:8] 33 21 mfr_iout_min1[7:0] 34 22 mfr_iout_min1[15:8] 35 23 mfr_vout_peak2[7:0] 36 24 mfr_vout_peak2[15:8] 37 25 mfr_vout_min2[7:0] 38 26 mfr_vout_min2[15:8] 39 27 mfr_temperature_ peak2[7:0] 40 28 mfr_temperature_ peak2[15:8] 41 29 mfr_temperature_ min2[7:0] 42 2a mfr_temperature_ min2[15:8] 43 2b mfr_iout_peak2[7:0] 44 2c mfr_iout_peak2[15:8] 45 2d mfr_iout_min2[7:0] 46 2e mfr_iout_min2[15:8] 47 2f mfr_vout_peak3[7:0] 48 30 mfr_vout_peak3[15:8] 49 31 mfr_vout_min3[7:0] 50 32 mfr_vout_min3[15:8] 51 33 mfr_temperature_ peak3[7:0] 52 34 mfr_temperature_ peak3[15:8] 53 35 mfr_temperature_ min3[7:0] 54 36 mfr_temperature_ min3[15:8] 55 37 mfr_iout_peak3[7:0] 56 38 mfr_iout_peak3[15:8] 57 39 mfr_iout_min3[7:0] 58 3a mfr_iout_min3[15:8] 59 3b status_vout0[7:0]
ltc2974 75 2974fa for more information www.linear.com/ltc2974 preamble information byte number decimal byte number hex d ata description 60 3c status_iout0[7:0] 61 3d status_ temperature0[7:0] 62 3e status_vout1[7:0] 63 3f status_iout1[7:0] 64 40 status_ temperature1[7:0] 65 41 status_vout2[7:0] 66 42 status_iout2[7:0] 67 43 status_ temperature2[7:0] 68 44 status_vout3[7:0] 69 45 status_iout3[7:0] 70 46 status_ temperature3[7:0] end of preamble cyclical mux loop data byte number decimal byte number hex loop byte number decimal mux loop 0 54 bytes per loop 71 47 13 read_pout0[15:8] position_last 72 48 12 read_pout0[7:0] 73 49 11 read_iout0[15:8] 74 4a 10 read_iout0[7:0] 75 4b 9 status_iout0[7:0] 76 4c 8 status_ temperature0[7:0] 77 4d 7 read_ temperature_1_0[15:8] 78 4e 6 read_ temperature_1_0[7:0] 79 4f 5 status_mfr_ specific0[7:0] 80 50 4 status_vout0[7:0] 81 51 3 read_vout0[15:8] 82 52 2 read_vout0[7:0] 83 53 1 read_ temperature_2[15:8] 84 54 0 read_ temperature_2[7:0] pmbus command description cyclical mux loop data byte number decimal byte number hex loop byte number decimal mux loop 1 54 bytes per loop 85 55 53 read_pout3[15:8] 86 56 52 read_pout3[7:0] 87 57 51 read_iout3[15:8] 88 58 50 read_iout3[7:0] 89 59 49 status_iout3[7:0] 90 5a 48 status_ temperature3[7:0] 91 5b 47 read_ temperature_1_3[15:8] 92 5c 46 read_ temperature_1_3[7:0] 93 5d 45 status_mfr_ specific3[7:0] 94 5e 44 status_vout3[7:0] 95 5f 43 read_vout3[15:8] 96 60 42 read_vout3[7:0] 97 61 41 read_pout2[15:8] 98 62 40 read_pout2[7:0] 99 63 39 read_iout2[15:8] 100 64 38 read_iout2[7:0] 101 65 37 status_iout2[7:0] 102 66 36 status_ temperature2[7:0] 103 67 35 read_ temperature_1_2[15:8] 104 78 34 read_ temperature_1_2[7:0] 105 69 33 status_mfr_ specific2[7:0] 106 6a 32 status_vout2[7:0] 107 6b 31 read_vout2[15:8] 108 6c 30 read_vout2[7:0] 109 6d 29 read_pout1[15:8] 110 6e 28 read_pout1[7:0] 111 6f 27 read_iout1[15:8] 112 70 26 read_iout1[7:0] 113 71 25 status_iout1[7:0] 114 72 24 status_ temperature2[7:0] 115 73 23 read_ temperature_1_1[15:8]
ltc2974 76 2974fa for more information www.linear.com/ltc2974 pmbus command description cyclical mux loop data byte number decimal byte number hex loop byte number decimal mux loop 1 54 bytes per loop 116 74 22 read_ temperature_1_1[7:0] 117 75 21 status_mfr_ specific1[7:0] 118 76 20 status_vout1[7:0] 119 77 19 read_vout1[15:8] 120 78 18 read_vout1[7:0] 121 79 17 0x0 122 7a 16 status_input[7:0] 123 7b 15 read_vin[15:8] 124 7c 14 read_vin[7:0] 125 7d 13 read_pout0[15:8] 126 7e 12 read_pout0[7:0] 127 7f 11 read_iout0[15:8] 128 80 10 read_iout0[7:0] 129 81 9 status_iout0[7:0] 130 82 8 status_ temperature0[7:0] 131 83 7 read_ temperature_1_0[15:8] 132 84 6 read_ temperature_1_0[7:0] 133 85 5 status_mfr_ specific0[7:0] 134 86 4 status_vout0[7:0] 135 87 3 read_vout0[15:8] 136 88 2 read_vout0[7:0] 137 89 1 read_ temperature_2[15:8] 138 8a 0 read_ temperature_2[7:0] cyclical mux loop data byte number decimal byte number hex loop byte number decimal mux loop 2 54 bytes per loop 139 8b 53 read_pout3[15:8] 140 8c 52 read_pout3[7:0] 141 8d 51 read_iout3[15:8] 142 8e 50 read_iout3[7:0] 143 8f 49 status_iout3[7:0] cyclical mux loop data byte number decimal byte number hex loop byte number decimal mux loop 2 54 bytes per loop 144 90 48 status_ temperature3[7:0] 145 91 47 read_ temperature_1_3[15:8] 146 92 46 read_ temperature_1_3[7:0] 147 93 45 status_mfr_ specific3[7:0] 148 94 44 status_vout3[7:0] 149 95 43 read_vout3[15:8] 150 96 42 read_vout3[7:0] 151 97 41 read_pout2[15:8] 152 98 40 read_pout2[7:0] 153 99 39 read_iout2[15:8] 154 9a 38 read_iout2[7:0] 155 9b 37 status_iout2[7:0] 156 9c 36 status_ temperature2[7:0] 157 9d 35 read_ temperature_1_2[15:8] 158 9e 34 read_ temperature_1_2[7:0] 159 9f 33 status_mfr_ specific2[7:0] 160 a0 32 status_vout2[7:0] 161 a1 31 read_vout2[15:8] 162 a2 30 read_vout2[7:0] 163 a3 29 read_pout1[15:8] 164 a4 28 read_pout1[7:0] 165 a5 27 read_iout1[15:8] 166 a6 26 read_iout1[7:0] 167 a7 25 status_iout1[7:0] 168 a8 24 status_ temperature2[7:0] 169 a9 23 read_ temperature_1_1[15:8] 170 aa 22 read_ temperature_1_1[7:0] 171 ab 21 status_mfr_ specific1[7:0] 172 ac 20 status_vout1[7:0] 173 ad 19 read_vout1[15:8]
ltc2974 77 2974fa for more information www.linear.com/ltc2974 pmbus command description cyclical mux loop data byte number decimal byte number hex loop byte number decimal mux loop 2 54 bytes per loop 174 ae 18 read_vout1[7:0] 175 af 17 0x0 176 b0 16 status_input[7:0] 177 b1 15 read_vin[15:8] 178 b2 14 read_vin[7:0] 179 b3 13 read_pout0[15:8] 180 b4 12 read_pout0[7:0] 181 b5 11 read_iout0[15:8] 182 b6 10 read_iout0[7:0] 183 b7 9 status_iout0[7:0] 184 b8 8 status_ temperature0[7:0] 185 b9 7 read_ temperature_1_0[15:8] 186 ba 6 read_ temperature_1_0[7:0] 187 bb 5 status_mfr_ specific0[7:0] 188 bc 4 status_vout0[7:0] 189 bd 3 read_vout0[15:8] 190 be 2 read_vout0[7:0] 191 bf 1 read_ temperature_2[15:8] 192 c0 0 read_ temperature_2[7:0] cyclical mux loop data byte number decimal byte number hex loop byte number decimal mux loop 3 54 bytes per loop 193 c1 53 read_pout3[15:8] 194 c2 52 read_pout3[7:0] 195 c3 51 read_iout3[15:8] 196 c4 50 read_iout3[7:0] 197 c5 49 status_iout3[7:0] 198 c6 48 status_ temperature_3[7:0] 199 c7 47 read_ temperature_1_3[15:8] 200 c8 46 read_ temperature_1_3[7:0] cyclical mux loop data byte number decimal byte number hex loop byte number decimal mux loop 3 54 bytes per loop 201 c9 45 status_mfr_ specific3[7:0] 202 ca 44 status_vout3[7:0] 203 cb 43 read_vout3[15:8] 204 cc 42 read_vout3[7:0] 205 cd 41 read_pout2[15:8] 206 ce 40 read_pout2[7:0] 207 cf 39 read_iout2[15:8] 208 d0 38 read_iout2[7:0] 209 d1 37 status_iout2[7:0] 210 d2 36 status_ temperature2[7:0] 211 d3 35 read_ temperature_1_2[15:8] 212 d4 34 read_ temperature_1_2[7:0] 213 d5 33 status_mfr_ specific2[7:0] 214 d6 32 status_vout2[7:0] 215 d7 31 read_vout2[15:8] 216 d8 30 read_vout2[7:0] 217 d9 29 read_pout1[15:8] 218 da 28 read_pout1[7:0] 219 db 27 read_iout1[15:8] 220 dc 26 read_iout1[7:0] 221 dd 25 status_iout1[7:0] 222 de 24 status_ temperature2[7:0] 223 df 23 read_ temperature_1_1[15:8] 224 e0 22 read_ temperature_1_1[7:0] 225 e1 21 status_mfr_ specific1[7:0] 226 e2 20 status_vout1[7:0] 227 e3 19 read_vout1[15:8] 228 e4 18 read_vout1[7:0] 229 e5 17 0x0 230 e6 16 status_input[7:0] 231 e7 15 read_vin[15:8] 232 e8 14 read_vin[7:0]
ltc2974 78 2974fa for more information www.linear.com/ltc2974 pmbus command description cyclical mux loop data byte number decimal byte number hex loop byte number decimal mux loop 3 54 bytes per loop 233 e9 13 read_pout0[15:8] 234 ea 12 read_pout0[7:0] 235 eb 11 read_iout0[15:8] 236 ec 10 read_iout0[7:0] 237 ed 9 status_iout0[7:0] last valid fault log byte 238 ee 0x00 bytes ee - fe return 0x00 239 ef 0x00 240 f0 0x00 241 f1 0x00 242 f2 0x00 243 f3 0x00 244 f4 0x00 245 f5 0x00 246 f6 0x00 247 f7 0x00 248 f8 0x00 249 f9 0x00 250 fa 0x00 251 fb 0x00 252 fc 0x00 253 fd 0x00 254 fe 0x00 this is pmbus byte 255. it must be read to clear mfr_fault_log_ status_ram. identification/information command name cmd code description type paged format units eeprom default value ref page capability 0x19 summary of pmbus optional communication protocols supported by this device. r byte n reg 0xb0 79 pmbus_revision 0x98 pmbus revision supported by this device. current revision is 1.1. r byte n reg 0x11 79 mfr_special_id 0xe7 manufacturer code for identifying the ltc2974. r word n reg y 0x0213 79 mfr_special_lot 0xe8 customer dependent codes that identify the factory programmed user configuration stored in eeprom. contact factory for default value. r byte y reg y 79
ltc2974 79 2974fa for more information www.linear.com/ltc2974 capability the capability command provides a way for a host system to determine some key capabilities of the ltc2974. capability data contents bit(s) symbol operation b[7] capability_pec hard coded to 1 indicating packet error checking is supported. reading the mfr_config_all_pec_en bit will indicate whether pec is currently required. b[6:5] capability_scl_max hard coded to 01b indicating the maximum supported bus speed is 400khz. b[4] capability_smb_alert hard coded to 1 indicating this device does have an alertb pin and does support the smbus alert response protocol. b[3:0] reserved always returns 0. pmbus_revision pmbus_revision data contents bit(s) symbol operation b[7:0] pmbus_rev reports the pmbus standard revision compliance. this is hard-coded to 0x11 for revision 1.1. mfr_special_id this register contains the manufacturer id for the ltc2974. always returns 0x0213. mfr_special_lot these paged registers contain information that identifies the user configuration that was programmed at the factory. contact the factory to request a custom factory programmed user configuration and special lot number. pmbus command description user_data_00, user_data_01, user_data_02, user_data_03, user_data_04, mfr_ltc_reserved_1 and mfr_ltc_reserved_2 these registers are provided as user scratchpad and additional manufacturer reserved locations. user_data_03 and user_data_04 are available for user scratch pad use. these 10 bytes (1 unpaged word plus 4 paged words) might be used for traceability or revision information such as serial number, board model number, assembly location, or assembly date. user scratchpad command name cmd code description type paged format units eeprom default value ref page user_data_00 0xb0 manufacturer reserved for ltpowerplay. r/w word n reg y n/a 79 user_data_01 0xb1 manufacturer reserved for ltpowerplay. r/w word y reg y n/a 79 user_data_02 0xb2 oem reserved. r/w word n reg y n/a 79 user_data_03 0xb3 scratchpad location. r/w word y reg y 0x00 79 user_data_04 0xb4 scratchpad location. r/w word n reg y 0x00 79 mfr_ltc_reserved_1 0xb5 manufacturer reserved. r/w word y reg y na 79 mfr_ltc_reserved_2 0xbc manufacturer reserved. r/w word y reg na 79
ltc2974 80 2974fa for more information www.linear.com/ltc2974 v pwr v dd33 v dd33 v dd25 v dd25 v in_sns ltc2974* 0.1f 0.1f 4.5v < v pwr < 15v gnd 0.1f *some details omitted for clarity 2978 f23 applications information overview the ltc2974 is a power management ic that is capable of sequencing, margining, trimming, supervising output voltage for ov/uv conditions, supervising output current for oc/uc conditions, fault management, and voltage/ current/temperature readback for four dc/dc converter channels. input voltage and ltc2974 junction temperature readback are also available. linear technology power system managers can coordinate operation among mul - tiple devices using common share_clk, faultb, and control pins. the ltc2974 utilizes a pmbus compliant interface and command set. powering the ltc2974 the ltc2974 can be powered two ways. the first method requires that a voltage between 4.5v and 15v be applied to the v pwr pin. see figure 23. an internal linear regula- tor converts v pwr down to 3.3v which drives all of the internal circuitry of the ltc2974. alternatively, power from an external 3.3v supply may be applied directly to the v dd33 pins 11 and 12 using a voltage between 3.13v and 3.47v. see figure 24. tie v pwr to the figure 23. powering ltc2974 directly from an intermediate bus v dd33 pins. all functionality is available when using this alternate power method. the higher voltages needed for the v out_en pins and bias for the v sense pins are charge pumped from v dd33 . setting command register values the command register settings described herein are in- tended as a reference and for the purpose of understanding the registers in a software development environment. in actual practice, the ltc2974 can be completely configured for stand-alone operation with the ltc usb to i 2 c/smbus/ pmbus controller (dc1613) and software gui using intui - tive menu driven objects. sequence, servo, margin and restart operations command units on or off three control parameters determine how a particular chan - nel is turned on and off: the control pins, the operation command and the value of the input voltage measured at the v in_sns pin (v in ). in all cases, vin must exceed vin_on in order to enable the device to respond to the control pins or operation commands. when v in drops below vin_off an immediate off or sequence off after toff_delay of all channels will result (see mfr_config_track_en n ). refer to the operation section in the data sheet for a detailed description of the on_off_config command. some examples of typical on/off configurations are: 1. a dc/dc converter may be configured to turn on any time v in exceeds vin_on. 2. a dc/dc converter may be configured to turn on only when it receives an operation command. 3. a dc/dc converter may be configured to turn on only via the control pin. 4. a dc/dc converter may be configured to turn on only when it receives an operation command and the control pin is asserted. on sequencing the ton_delay command sets the amount of time that v dd33 v dd33 v dd25 v dd25 v pwr ltc2974* 0.1f 0.1f gnd *some details omitted for clarity 2978 f24 external 3.3v figure 24. powering ltc2974 from external 3.3v supply
ltc2974 81 2974fa for more information www.linear.com/ltc2974 applications information a channel will wait following the start of an on sequence before its v out_en pin will enable a dc/dc converter. once the dc/dc converter has been enabled, the ton_rise value determines the time at which the device soft-connects the dac and servos the dc/dc converter output to the vout_command value. the ton_max_fault_limit value determines the time at which the device checks for an undervoltage condition. if a ton_max_fault oc - curs, the channel can be configured to disable the dc/dc converter and propagate the fault to other channels using the bidirectional faultb pins. figure 25 shows a typical on-sequence using the control pin. note that overvolt- age faults are checked against the vout_ov_fault_limit value at all times the device is powered up and not in a reset state nor margining while ignoring ovs. on state operation once a channel has reached the on state, the opera - tion command can be used to command the dc/dc converters output to margin high, margin low, or return to a nominal output voltage indicated by vout_command. the user also has the option of configuring a channel to continuously trim the output of the dc/dc converter to the vout_command voltage, or the channels v dacn output figure 25. typical on sequence using control pin vout_ov_fault_limit vout_uv_fault_limit v control v out_en v out ton_delay ton_rise 2974 f25 v dc(nom) v out_command ton_max_fault_limit can be placed in a high impedance state thus allowing the dc/dc converter output voltage to go to its nominal value, v dc n (nom) . refer to the mfr_config_ltc2974 command for details on how to configure the output voltage servo. servo modes the adc, dac and internal processor comprise a digital servo loop that can be configured to operate in several useful modes. the servo target refers to the desired output voltage. continuous/non-continuous trim mode: mfr_ config_ltc2974 b[7]. in continuous trim mode, the servo will update the dac in a closed loop fashion each time it takes a v out reading. the update rate is determined by the time it takes to step through the adc mux which is no more than t update_adc . see electrical characteristics table note?5. in non-continuous trim mode, the servo will drive the dac until the adc measures the output voltage desired and then stop updating the dac. non-continuous servo on warn mode: mfr_config_ ltc2974 b[7] = 0, b[6] = 1. when in non-continuous mode, the ltc2974 will re-trim (re-servo) the output if the output drifts beyond the ov or uv warn limits.
ltc2974 82 2974fa for more information www.linear.com/ltc2974 applications information dac modes the dacs that drive the v dacn pins can operate in several useful modes. see mfr_config_ltc2974. ? soft-connect. using the ltc patented soft-connect feature, the dac output is driven to within 1 lsb of the voltage at the dc/dcs feedback node before con - necting, to avoid introducing transients on the output. this mode is used when servoing the output voltage. during startup, the ltc2974 waits until ton_rise has expired before connecting the dac. this is the most common operating mode. ? disconnected. dac output is high z. ? dac manual with soft-connect. non servo mode. the dac soft-connects to the feedback node. soft-connect drives the dac code to match the voltage at the feedback node. after connection, the dac is moved by writing dac codes to the mfr_dac register. ? dac manual with hard connect. non servo mode. the dac hard connects to the feedback node using the cur - rent value in mfr_dac. after connection, the dac is moved by writing dac codes to the mfr_dac register. margining the ltc2974 margins and trims the output of a dc/dc converter by forcing a voltage across an external resistor connected between the dac output and the feedback node or the trim pin. preset limits for margining are stored in the vout_margin_high/low registers. margining is actuated by writing the appropriate bits to the opera- tion register. margining requires the dac to be connected. margin requests that occur when the dac is disconnected will be ignored. off sequencing an off sequence is initiated using the control pin or the operation command. the toff_delay value determines the amount of time that elapses from the beginning of the off sequence until each channels v out_en pin is pulled low, thus disabling its dc/dc converter. v out off threshold voltage the mfr_vout_discharge_threshold command register allows the user to specify the off threshold that the output voltage must decay below before the channel can enter/re-enter the on state. the off threshold voltage is specified by multiplying mfr_vout_discharge_ threshold and vout_command. in the event that an output voltage has not decayed below its off threshold before attempting to enter the on state, the channel will continue to be held off, the appropriate bit is set in the status_mfr_specific register, and the alertb pin will be asserted low. when the output voltage has decayed below its off threshold, the channel can enter the on state. automatic restart via mfr_restart_delay command and control pin an automatic restart sequence can be initiated by driving the control pin to the off state for >10s and then re - leasing it. the automatic restart disables all v out_en pins that are mapped to a particular control pin for a time period = mfr_restart_delay and then starts all dc/ dc converters according to their respective ton_delays. (see figure 26). v out_en pins are mapped to one of the control pins by the mfr_config_ltc2974 command. this feature allows a host that is about to reset to restart the power in a controlled manner after it has recovered. figure 26. off sequence with automatic restart v control v out_en0 control pin bounce toff_delay0 ton_delay0 2974 f26 mfr_restart_delay fault management output overvoltage, undervoltage, overcurrent, and undercurrent faults the high-speed voltage supervisor ov and uv fault thresh - olds are configured using the vout_ov_fault_limit and vout_uv_fault_limit commands, respectively. the vout_ov_fault_response and vout_uv_fault_ response registers determine the responses to
ltc2974 83 2974fa for more information www.linear.com/ltc2974 applications information ov/uv faults. in addition, the high-speed current supervi - sor oc and uc fault thresholds are configured using the iout_oc_fault_limit and iout_uc_fault_limit com - mands, respectively. the iout_oc_fault_response and iout_uc_fault_response commands determine the responses to oc/uc faults. fault responses can range from disabling the dc/dc converter immediately, waiting to see if the fault condition persists for some interval be - fore disabling the dc/dc converter, or allowing the dc/dc converter to continue operating in spite of the fault. if a dc/dc converter is disabled, the ltc2974 can be config - ured to retry one to six times, retry continuously without limitation, or latch-off. the retry interval is specified using the mfr_retry_delay command. latched faults are reset by toggling the control pin, using the operation command, or removing and reapplying the bias voltage to the v in_sns pin. all fault and warning conditions result in the alertb pin being asserted low and the corresponding bits being set in the status registers. the clear_faults command resets the contents of the status registers and de-asserts the alertb output. output overvoltage, undervoltage, and overcurrent warnings ov, uv, and oc warning thresholds are processed by the ltc2974s adc. these thresholds are set by the vout_ov_warn_limit, vout_uv_warn_limit, and iout_oc_warn_limit registers, respectively. note that there is no i out uc warning threshold. if a warning occurs, the corresponding bits are set in the status registers and the alertb output is asserted low. note that a warning will never cause a v out_en output pin to disable a dc/dc converter. configuring the auxfaultb output the auxfaultb output may be used to indicate an output ov, oc, or uc fault. use the mfr_config2_ltc2974 and mfr_config3_ltc2974 registers to configure the auxfaultb pin to assert low in response to vout_ov, iout_oc or iout_uc fault conditions. the auxfaultb output will stop pulling low when the ltc2974 is com - manded to re-enter the on state following a faulted-off condition. a charge-pumped 5a pull-up to 12v is also available on the auxfaultb output. refer to the mfr_config_all_ ltc2974 register description in the pmbus command description section for more information. figure 27 shows an application circuit where the aux - faultb output is used to trigger a scr crowbar on the intermediate bus in order to protect the dc/dc converters load from a catastrophic fault such as a stuck top-gate. figure 27. application circuit with crowbar protection on intermediate bus 0.1f v pwr auxfaultb v in_sns v dac0 v sensep0 v sensem0 v out_en0 ltc2974* 4.5v < v ibus < 15v v dd33 v dd33 *some details omitted for clarity only one of four channels shown v in c bypass 0.1f 0.01f 0.22f 0.01f 220 mcr12dc 0.1f v dd25 v dd25 v out 2974 f27 run/ss sgnd v fb gnd dc/dc converter load 4.99k 10k 100 68 v cc sense r sense 0.007 q1 si4894bdy ltc4210-1 timer gnd gate 24.3k 10k on 0.01f mmbt2907 refp refm gnd
ltc2974 84 2974fa for more information www.linear.com/ltc2974 applications information multi-channel fault management multi-channel fault management is handled using the bidirectional faultb pins. figure 28 illustrates the con - nections between channels and the faultb pins. ? the mfr_faultb n _propagate register acts like a programmable switch that allows faulted_off conditions from a particular channel (page) to propagate to either faultb output. the mfr_faultb n _response register controls similar switches on the inputs to each channel that allow any channel to shut down in response to any combination of the faultb pins. channels responding to a faultb pin pulling low will attempt a new start sequence when the faultb pin in question is released by the faulted channel. ? a faultb pin can also be asserted low by an external driver in order to initiate an immediate off-sequence after a 10s deglitch delay. interconnect between multiple ltc2974s figure 29 shows how to interconnect the pins in a typical multi-ltc2974 array. ? all v in_sns lines should be tied together in a star type connection at the point where v in is to be sensed. this will minimize timing errors for the case where the on_off_config is configured to start the ltc2974 based on v in and ignore the control line and the operation figure 28. channel fault management block diagram command. in multi-part applications that are sensitive to timing differences, it is recommended that the vin_share_ enable bit of the mfr_config_all_ltc2974 register be set high in order to allow share_clk to synchronize on/ off sequencing in response to the vin_on and vin_off thresholds. ? connecting all auxf aultb lines together will allow selected faults on any dc/dc converters output in the array to shut off a common input switch. ? alertb is typically one line in an array of pmbus con - verters. the ltc2974 allows a rich combination of faults and warnings to be propagated to the alertb pin. ? wdi/resetb can be used to put the ltc2974 in the power-on reset state. pull wdi/resetb low for at least t resetb to enter this state. ? the faultb lines can be connected together to create fault dependencies. figure 29 shows a configuration where a fault on any faultb will pull all others low. this is useful for arrays where it is desired to abort a startup sequence in the event any channel does not come up (see figure 30). ? pwrgd reflects the status of the outputs that are mapped to it by the mfr_pwrgd_en command. fig - ure 29 shows all the pwrgd pins connected together, but any combination may be used. channel 0 event processor page = 0 mfr_faultb0_response, page = 0 mfr_faultb1_response, page = 0 mfr_faultb0_propagate_chan0 faultb0 faulted_off faulted_off faulted_off faulted_off mfr_faultb1_propagate_chan0 channel 1 event processor page = 1 mfr_faultb0_response, page = 1 mfr_faultb1_response, page = 1 mfr_faultb0_propagate_chan1 mfr_faultb1_propagate_chan1 channel 2 event processor page = 2 mfr_faultb0_response, page = 2 mfr_faultb1_response, page = 2 mfr_faultb0_propagate_chan2 mfr_faultb1_propagate_chan2 channel 3 event processor page = 3 mfr_faultb0_response, page = 3 mfr_faultb1_response, page = 3 mfr_faultb0_propagate_chan3 mfr_faultb1_propagate_chan3 faultb1 2974 f28
ltc2974 85 2974fa for more information www.linear.com/ltc2974 applications information figure 29. typical connections between multiple ltc2974s figure 30. aborted on-sequence due to channel 1 short vin_sns auxfaultb sda scl alertb control0 wdi/resetb faultb0 share_clk pwrgd gnd ltc2974 #1 vin_sns auxfaultb sda scl alertb control0 wdi/resetb faultb0 share_clk pwrgd gnd 2974 f29 ltc2974 #n to v in of dc/dcs to input switch to host controller to other ltc2974s?10k equivalent pull-up recommended on each line except share_clk (use 5.49k) v control v out0 ton_delay0 v out1 v out2 v outn bussed v faultb n pins ton_max_fault1 2974 f30 ton_delay1 ton_delay2 ton_delay n ? ? ? ? ? ? application circuits trimming and margining dc/dc converters with external feedback resistors figure 31 shows a typical application circuit for trimming/ margining a power supply with an external feedback network. the v sensep0 and v sensem0 differential inputs sense the load voltage directly, and a correction voltage is developed on the v dac0 pin by the closed-loop servo algorithm. the v dac0 output is connected to the dc/dc converters feedback node through resistor r30. for this configuration, set mfr_config_dac_pol to 0. four-step resistor selection procedure for dc/dc converters with external feedback resistors the following four-step procedure should be used to calculate the resistor values required for the application circuit shown in figure 31. 1. assume values for feedback resistor r20 and the nominal dc/dc converter output voltage v dc(nom) , and solve for r10. v dc(nom) is the output voltage of the dc/dc converter when the ltc2974s v dac0 pin is in a high impedance
ltc2974 86 2974fa for more information www.linear.com/ltc2974 applications information figure 31. application circuit for dc/dc converters with external feedback resistors v pwr v dd33 v dd33 v dd25 v dd25 v in_sns v dac0 v sensep0 v sensem0 v out_en0 ltc2974* 0.1f 0.1f 4.5v < v ibus < 15v gnd *some details omitted for clarity only one of four channels shown v in v out r20 r30 r10 2974 f31 run/ss sgnd v fb gnd dc/dc converter load state. r10 is a function of r20, v dc(nom) , the voltage at the feedback node (v fb ) when the loop is in regulation, and the feedback nodes input current (i fb ). r10 = r20 ? v fb v dc(nom) C i fb ? r20 C v fb (1) 2. solve for the value of r30 that yields the maximum required dc/dc converter output voltage v dc(max) . when v dac0 is at 0v, the output of the dc/dc converter is at its maximum voltage. r30 r20 ? v fb v dc(max) C v dc(nom) (2) 3. solve for the minimum value of v dac0 that is needed to yield the minimum required dc/dc converter output voltage v dc(min) . the dac has two full-scale settings, 1.38v and 2.65v. in order to select the appropriate full-scale setting, calculate the minimum required v dac0(f/s) output voltage: v dac0(f/s) > v dc(nom) C v dc(min) ( ) ? r30 r20 + v fb (3) 4. re-calculate the minimum, nominal, and maximum dc/dc converter output voltages and the resulting margining resolution. v dc(nom) = v fb ? 1 + r20 r10 ? ? ? ? ? ? + i fb ? r20 (4) v dc(min) = v dc(nom) C r20 r30 ? v dac0(f /s) C v fb ( ) (5) v dc(max) = v dc(nom) + r20 r30 ? v fb (6) v res = r20 r30 ? v dac0(f /s) 1024 v/dac lsb (7) trimming and margining dc/dc converters with a trim pin figure 32 illustrates a typical application circuit for trim - ming/margining the output voltage of a dc/dc converter with a trim pin. the ltc2974s v dac0 pin connects to the trim pin through resistor r30. for this configuration, set the dac polarity bit mfr_config_dac_pol in mfr_con - fig_ltc2974 to 1.
ltc2974 87 2974fa for more information www.linear.com/ltc2974 applications information dc/dc converters with a trim pin may be margined high or low by connecting an external resistor between the trim pin and either the v sensep or v sensem pin. the relationships between these resistors and the ? % change in the output voltage of the dc/dc converter are typically expressed as: r trim _ down = r trim ? 50 ? down % C r trim (8) r trim _ up = r trim ? v dc ? 100 + ? up % ( ) 2 ? v ref ? ? up % C 50 ? up % ? ? ? ? ? ? C 1 ? ? ? ? ? ? (9) where r trim is the resistance looking into the trim pin, v ref is the trim pins open-circuit output voltage and v dc is the dc/dc converters nominal output voltage. ? up % and ? down % denote the percentage change in the converters output voltage when margining up or down, respectively. two-step resistor and dac full-scale voltage selection procedure for dc/dc converters with a trim pin the following two-step procedure should be used to cal - culate the resistor value for r30 and the required full-scale dac voltage (refer to figure 32). 1. solve for r30: r30 r trim ? 50 C ? down % ? down % ? ? ? ? ? ? (10) 2. calculate the maximum required output voltage for v dac0 : v dac 0 1 + ? up % ? down % ? ? ? ? ? ? ? v ref (11) note: not all dc/dc converters follow these trim equations, especially newer bricks. consult ltc field application engineering. figure 32. application circuit for dc/dc converters with trim pin v pwr v dd33 v dd33 v dd25 v dd25 v in_sns v dac0 v sensep0 v sensem0 v out_en0 ltc2974* 0.1f 0.1f 4.5v < v ibus < 15v gnd *some details omitted for clarity only one of four channels shown v in v o + r30 2974 f32 on/offb v sense ? v sense + trim v o ? dc/dc converter load
ltc2974 88 2974fa for more information www.linear.com/ltc2974 applications information measuring current with a sense resistor a circuit for measuring current with a sense resistor is shown in figure 33. the balanced filter rejects both com - mon mode and differential mode noise from the output of the dc/dc converter. the filter is placed directly across the sense resistor in series with the dc/dc converters in - ductor. note that the current sense inputs must be limited to less than 6v with respect to ground. select r cm and c cm such that the filters corner frequency is < 1/10 the dc/dc converters switching frequency. this will result in a current sense waveform that offers a good compromise between the voltage ripple and the delay through the filter. a value 1k for r cm is suggested in order to minimize gain errors due to the current sense inputs internal resistance. measuring current with inductor dcr figure 34 shows the circuit for applications that require dcr current sense. a second order r-c filter is required in these applications in order to minimize the ripple volt - age seen at the current sense inputs. a value of 1k is suggested for r cm1 and r cm2 in order to minimize gain errors due the current sense inputs internal resis - tance. c cm1 should be selected to provide cancellation of the zero created by the dcr and inductance, i.e. c cm1 = l/(dcr?? r cm1 ). c cm2 should be selected to provide a second stage corner frequency at < 1/10 of the dc/dc converters switching frequency. in addition, c cm2 needs to be much smaller than c cm1 in order to prevent significant loading of the filters first stage. single phase design example as a design example for a dcr current sense application, assume l = 2.2h, dcr = 10m, and f sw = 500khz. let r cm1 = 1k and solve for c cm1 : c cm1 2.2h 10m ? ? 1k ? = 220nf let r cm2 = 1k. in order to get a second pole at f sw /10 = 50khz: c cm2 ? 1 2 ? 50khz ? 1k ? = 3.18nf let c cm2 = 3.3nf. note that since c cm2 is much less than c cm1 the loading effects of the second stage filter on the matched first stage are not significant. consequently, the delay time constant through the filter for the current sense waveform will be approximately 3s. measuring multiphase currents for current sense applications with more than one phase, r-c averaging may be employed. figure 35 shows an example of this approach for a 3-phase system with dcr current sensing. the current sense waveforms are aver - aged together prior to being applied to the second stage of the filter consisting of r cm2 and c cm2 . because the r cm1 resistors for the three phases are in parallel, the value of r cm1 must be multiplied by the number of phases. also note that since the dcrs are effectively in parallel, the value for iout_cal_gain will be equal to the inductors dcr divided by the number of phases. care should be taken in the layout of the multiphase inductors to keep the pcb trace resistance from the dc side of each inductor to the summing node balanced in order to provide the most accurate results. figure 33.sense resistor current sensing circuits figure 34. dcr current sensing circuits r cm r cm r sns 2974 f33 l load current c cm c cm ltc2974 i sensep i sensem 2974 f34 r cm2 r cm2 r cm1 r cm1 dcr l c cm2 c cm2 ltc2974 i sensep i sensem c cm1 c cm1 swx0
ltc2974 89 2974fa for more information www.linear.com/ltc2974 ltc2974 i sensep i sensem 2974 f35 c cm2 c cm2 r cm2 c cm2 c cm1 r cm2 r cm1 r cm1 r cm1 r cm1/3 dcr dcr l l dcr l swx2 swx3 to load swx1 figure 35. multiphase dcr current sensing circuits applications information multiphase design example using the same values for inductance and dcr from the previous design example, the value for r cm1 will be 3k for a three phase dc/dc converter if c cm1 is left at 220nf. similarly, the value for iout_cal_gain will be dcr/3?=?3.33m. anti-aliasing filter considerations noisy environments require an anti-aliasing filter on the input to the ltc2974s adc. the r-c circuit shown in figure 36 is adequate for most situations. keep r40 = r50 200? to minimize adc gain errors, and select a value for capacitors c10 and c20 that does not add too much additional response time to the ov/uv supervisor, e.g. = 10s (r = 100?, c = 0.10f). sensing negative voltages figure 37 shows the ltc2974 sensing a negative power supply (v ee ). the r1/r2 resistor divider translates the negative supply voltage to the ltc2974s v sensem1 input while the v sensep1 input is tied to the refp pin which has a typical output voltage of 1.23v. read_vout is determined from the following equation: v ee = v refp C read_ vout ( ) ? r2 r1 + 1 ? ? ? ? ? ? C 1a ? r2 (14) where read_vout returns v sensep C v sensem the voltage divider should be configured in order to present about 0.5v to the voltage sense inputs when the negative supply reaches its power_good_on threshold so that figure 36. anti-aliasing filter on v sense lines v pwr v dd33 v dd33 v dd25 v dd25 v in_sns v dac0 v sensep0 v sensem0 v out_en0 ltc2974* 0.1f 0.1f 4.5v < v ibus < 15v *some details omitted for clarity only one of four channels shown v in v out r20 r30 r10 2974 f36 run/ss sgnd v fb gnd dc/dc converter load c10 c20 r50 r40 gnd
ltc2974 90 2974fa for more information www.linear.com/ltc2974 applications information the current flowing out of the v sensemn pin is minimized to ~1a. the relationship between the power_good_on register value and the corresponding negative supply value can be determined using equation 14. connecting the dc1613 usb to i 2 c/smbus/pmbus controller to the ltc2974 in system the dc1613 usb to i 2 c/smbus/pmbus controller can be interfaced to the ltc2974s on the users board for programming, telemetry and system debug. the control - ler, when used in conjunction with ltpowerplay software, provides a powerful way to debug an entire power system. failures are quickly diagnosed using telemetry, fault status registers and the fault log. the final configuration can be quickly developed and stored to the ltc2974s eeprom. figure 38 and figure 39 illustrate application schematics for powering, programming and communicating with one or more ltc2974s via the dc1613 i 2 c/smbus/pmbus controller regardless of whether or not system power is present. figure 38 shows the recommended schematic to use when the ltc2974 is powered by the system intermediate bus through its v pwr pin. figure 39 shows the recommended schematic to use when the ltc2974 is powered by the system 3.3v through its v dd33 and v pwr pins. the ltc4412 ideal oring circuit allows either the controller or system to power the ltc2974. because of the controllers limited current sourcing capabil - ity, only the ltc2974s, their associated pull up resistors and the i 2 c/smbus pull-up resistors should be powered from the ored 3.3v supply. in addition, any device sharing i 2 c/smbus bus connections with the ltc2974 should not have body diodes between the sda/scl pins and its v dd node because this will interfere with bus communication in the absence of system power. the dc1613 controllers i 2 c/smbus connections are opto- isolated from the pcs usb port. the 3.3v supply from the controller and the ltc2974s v dd33 pin can be paralleled because the ltc ldos that generate these voltages can be backdriven and draw <10a. the controllers 3.3v current limit is 100ma. figure 37. sensing negative voltages ltc2974 4.5v < v ibus < 15v gnd only one of four channels shown, some details omitted for clarity power_good_on = 0.5v for v ee power_good = ?11.414v where v ee power_good = v refp C power_good_on (r2/r1 + 1) C 1a ? r2 0.1f 1.23v typ 2974 f37 v pwr sda scl alertb control faultb wdi/resetb share_clk asel0 asel1 wp v in_sns refm v sensep1 wdi/resetb v sensem1 refp pwrgd 0.1f r1 = 4.99k 1a at 0.5v r2 = 120k v ee = ?12v pmbus interface
ltc2974 91 2974fa for more information www.linear.com/ltc2974 figure 38. dc1613 controller connections when v pwr is used 2974 f38 v pwr v dd33 ltc2974* wp gnd *pin connections omitted for clarity repeat outlined circuit for every ltc2974 to/from other ltc2974s 0.1f 5.49k 10k 10k v dd33 0.1f v dd25 v dd25 0.1f 49.9k 150k scl sda share_clk to dc1613 i 2 c/smbus/pmbus controller isolated 3.3v si1303 4.5v to 15v scl gnd sda to dc1613 i 2 c/smbus/pmbus controller isolated 3.3v scl gnd sda 2974 f39 ltc4412 note: dc1613 controller i 2 c connections are opto-isolated isolated 3.3v from ltc controller can be back driven and will only draw <10a isolated 3.3v current limit is 100ma sense v in gate gnd stat ctl v pwr v dd33 ltc2974* wp gnd *pin connections omitted for clarity to/from other ltc2974s ideal diode or?d 3.3v tp0101k-sot23 system 3.3v 0.1f v dd33 v dd25 v dd25 0.1f scl sda share_clk applications information figure 39. dc1613 controller connections when ltc2974 is powered directly from 3.3v
ltc2974 92 2974fa for more information www.linear.com/ltc2974 applications information accurate dcr temperature compensation using the dc resistance of the inductor as a current shunt element has several advantages C no additional power loss, lower circuit complexity and cost. however, the strong temperature dependence of the inductor resistance and the difficulty in measuring the exact inductor core temperature introduce errors in the current measurement. for copper, a change of inductor temperature of only 1c corresponds to approximately 0.39% current gain change. figure 40 shows a sample layout using the integrated dc/dc converter ltc3601 (right) and its corresponding thermal image (left). the converter is providing 1.8v, 1.5a to the output load. heat dissipation in the inductor under high load condi - tions creates transient and steady state thermal gradients between the inductor and the temperature sensor, and the sensed temperature does not accurately represent the inductor core temperature. this temperature gradient is clearly visible in the thermal image of figure 40. in addition, transient heating/cooling effects have to be accounted for in order to reduce the transient errors introduced when load current changes are faster than heat transfer time constants of the inductor. both of these problems are addressed by introducing two additional parameters: the thermal resistance is from the inductor core to the on- board temperature sensor, and the inductor thermal time constant . the thermal resistance is [c/w], is used to calculate the steady state difference between the sensed temperature t s and the internal inductor temperature t i for a given power dissipated in the inductor p i : t i C t s = is p i = is v dcr i out (1.1) the additional temperature rise is used for a more accurate estimate of the inductor dc resistance r i : r i = r0 (1 + a [t s C t ref + is v dcr i out ]) (1.2) in the equations above, v dcr is the inductor dc voltage drop, i out is the rms value of the output current, r0 is the inductor dc resistance at the reference temperature t ref and a is the temperature coefficient of the resistance. since most inductors are made of copper, we can expect a temperature coefficient close to a cu = 3900ppm/c. for a given a , the remaining parameters is and r0 can be calibrated at a single temperature using only two load currents: r0 = r2 ? r1 ( ) p2 + p1 ( ) ? r2 + r1 ( ) p2 ? p1 ( ) a t2 ? t1 ( ) p2 + p1 ( ) ? p2 ? p1 ( ) 2 + a t1 + t2 ? 2t ref ? ? ? ? ( ) (1.3) is = 1 a r0 a r1 + r2 ( ) t2 ? t1 ( ) ? r2 ? r1 ( ) 2 + a t1 + t2 ? 2t ref ? ? ? ? ( ) a t2 ? t1 ( ) p2 + p1 ( ) ? p2 ? p1 ( ) 2 + a t1 + t2 ? 2t ref ? ? ? ? ( ) (1.4) 2974 f40 ltc3601 inductor temperature sensor figure 40. thermal image of a dc/dc converter showing the difference between the actual inductor temperature and the temperature sensing point
ltc2974 93 2974fa for more information www.linear.com/ltc2974 applications information the inductor resistance, r k = v dcr(k) /i out(k) , power dis - sipation p k = v dcr(k) i out(k) and the sensed temperature t k , (k = 1, 2) are recorded for each load current. to increase the accuracy in calculating is , the two load currents should be chosen around i1 = 10% and i2 = 90% of the current range of the system. the inductor thermal time constant models the first order thermal response of the inductor and allows accurate dcr compensation during load transients. during a transition from low to high load current, the inductor resistance increases due to the self-heating. if we apply a single load step from the low current i1 to the higher current i2, the voltage across the inductor will change instantaneously from i1r1 to i2r1 and then slowly approach i2r2. here r1 is the steady state resistance at the given temperature and load current i1, and r2 is the slightly higher dc resis - tance at i2, due to the inductor self-heating. note that the electrical time constant el = l/r is several orders of mag - nitude shorter than the thermal one, and instantaneous is relative to the thermal time constant. the two settled regions give us the data sets (i1, t1, r1, p1) and (i2, t2, r2, p2) and the two-point calibration technique (1.3-1.4) is used to extract the steady-state parameters is and r0 (given a previously characterized average a ). the relative current error calculated using the steady-state expression (1.2) will peak immediately after the load step, and then decay to zero with the inductor thermal time constant . ? i i (t) = a is v2 ? i2 ? v1 ? i1 ( ) e ? t/ (1.5) the time constant is calculated from the slope of the best-fit line y = ln(?i/i) = a1 + a2t: = ? 1 a2 (1.6) in summary, a single load current step is all that is needed to calibrate the dcr current measurement. the stable por - tions of the response give us the thermal resistance is and nominal dc resistance r0, and the settling characteristic is used to measure the inductor thermal time constant . to get the best performance, the temperature sensor has to be as close as possible to the inductor and away from other significant heat sources. for example in figure 40, the bipolar sense transistor is close to the inductor and away from the switcher. connecting the collector of the pnp to the local power ground plane assures good thermal contact to the inductor, while the base and emitter should be routed to the ltc2974 separately, and the base con - nected to the signal ground close to ltc2974. ltpowerplay : an interactive gui for power managers ltpowerplay is a powerful windows based development environment that supports linear technology power sys - tem manager ics with eeprom, including the ltc2974 4-channel pmbus power system manager. the software supports a variety of different tasks. you can use ltpow - erplay to evaluate linear technology ics by connecting to a demo board system. ltpowerplay can also be used in an offline mode (with no hardware present) in order to build a multi-chip configuration file that can be saved and re-loaded at a later time. ltpowerplay provides un - precedented diagnostic and debug features. it becomes a valuable diagnostic tool during board bring-up to program the power management scheme in a system. ltpowerplay utilizes linear technologys dc1613 usb-to-i 2 c/smbus/ pmbus controller to communicate with one of many potential targets, including the dc1809/dc1810 demo board set, the dc1735 socketed programming board, or a customer target system. the software also provides an automatic update feature to keep the software current with the latest set of device drivers and documentation. a great deal of context sensitive help is available within ltpowerplay along with several tutorial demos. complete information is available at: www.linear.com/ltpowerplay
ltc2974 94 2974fa for more information www.linear.com/ltc2974 pcb assembly and layout suggestions bypass capacitor placement the ltc2974 requires 0.1f bypass capacitors between the v dd33 pins and gnd, the v dd25 pin and gnd, and the refp pin and refm pin. if the chip is being powered from the v pwr input, then that pin should also be bypassed to gnd by a 0.1f capacitor. in order to be effective, these capacitors should be made of a high quality ceramic dielectric such as x5r or x7r and be placed as close to the chip as possible. exposed pad stencil design the ltc2974s package is thermally and electrically ef - ficient. this is enabled by the exposed die attach pad on the under side of the package which must be soldered applications information down to the pcb or mother board substrate. it is a good practice to minimize the presence of voids within the exposed pad inter-connection. total elimination of voids is difficult, but the design of the exposed pad stencil is key. figure 42 shows a suggested screen print pattern. the proposed stencil design enables out-gassing of the solder paste during reflow as well as regulating the finished solder thickness. see ipc7525a unused adc sense inputs connect all unused adc sense inputs (v sensep n , v sensemn , i sensepn or i sensemn ) to gnd. in a system where the inputs are connected to removable cards and may be left floating in certain situations, connect the inputs to gnd using 100k resistors. place the 100k resistors before any filter components, as shown in figure 41, to
ltc2974 95 2974fa for more information www.linear.com/ltc2974 figure 42. suggested screen pattern for die attach pad figure 41. connecting unused inputs to gnd 2974 f42 qfn package aperature design 50% to 80% reduction ground plane prevent loading of the filter. the temperature sense inputs (t sensen ) may be left floating. the temperture reported on floating t sense n inputs will be the internal die temperature (read_temperature_2). pcb board layout mechanical stress on a pc board and soldering-induced stress can cause the ltc2974s reference voltage and the voltage drift to shift. a simple way to reduce the stress- related shifts is to mount the ic near the short edge of the pc board, or in a corner. the board acts as a stress boundary, or a region where the flexure of the board is minimal. applications information 100k 100k v sensep v sensem ltc2974 2974 f41
ltc2974 96 2974fa for more information www.linear.com/ltc2974 package description 9 .00 0.10 (4 sides) note: 1. drawing conforms to jedec package outline mo-220 variation wnjr-5 2. all dimensions are in millimeters 3. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.20mm on any side, if present 4. exposed pad shall be solder plated 5. shaded area is only a reference for pin 1 location on the top and bottom of package 6. drawing not to scale pin 1 top mark (see note 5) 0.40 0.10 6463 1 2 bottom view?exposed pad 7.15 0.10 7.15 0.10 7.50 ref (4-sides) 0.75 0.05 r = 0.10 typ r = 0.115 typ 0.25 0.05 0.50 bsc 0.200 ref 0.00 ? 0.05 (up64) qfn 0406 rev c recommended solder pad pitch and dimensions apply solder mask to areas that are not soldered 0.70 0.05 7.50 ref (4 sides) 7.15 0.05 7.15 0.05 8.10 0.05 9.50 0.05 0.25 0.05 0.50 bsc package outline pin 1 chamfer c = 0.35 up package 64-lead plastic qfn (9mm 9mm) (reference ltc dwg # 05-08-1705 rev c) please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
ltc2974 97 2974fa for more information www.linear.com/ltc2974 information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa - tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. revision history rev date description page number a 5/13 title, features and description revised. added specifications: t init , t update_adc , t off_min . changed v fs_vdac minimums to 1.3 and 2.5 from 1.32 and 2.53. curve g08: corrected y-axis units from ma to a. block diagram revised. resetb section: clarified i 2 c disabled, 10k resistor and capacitance. typical delay numbers in eeprom related commands table updated. ton_rise description: changed output starts to rise to v out_enn pin goes high. changed data format for mfr_dac and mfr_i2c_base_address to reg from u16. changed default value for mfr_special_id to 0x0213 from 0x0212. removed u16 row from data formats table. operation, on_off_config sections: added sentence on waiting a t off_min . b[5:4] operation: added warning about undefined mfr_dac. b[3] to b[0] operation: clarified that setting these bits disables uv and uc. changed format for mfr_retry_count to reg from u16. status_vout b[3] operation: clarified behavior after bit is cleared. status_mfr_specific section: added sticky, alert, off columns; removed fault column. added column definitions above table. status_mfr_specific b[6] and b[5]: clarified behavior if mfr_track_en_chann is set. mfr_vout_min: clarified when updates are disabled. mfr_fault_log_clear: clarified conditions before issuing this command. mfr_special_id: changed value from 0x0210 to 0x0213. added section: unused adc sense inputs. 1 5, 9 6 10 15 18 19 24, 51 26, 44 27 30, 31 32 36 54 62 64 64 69 71 78, 79 94
ltc2974 98 2974fa for more information www.linear.com/ltc2974 ? linear technology corporation 2012 lt 0513 rev a ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com/ltc2974 related parts typical application part number description comments ltc2970 dual i 2 c power supply monitor and margining controller 5v to 15v, 0.5% tue 14-bit adc, 8-bit dac, temperature sensor ltc2977 8-channel pmbus power system manager 0.25% tue 16-bit adc, voltage/temperature monitoring and supervision ltc3880 dual output polyphase step-down dc/dc controller 0.5% tue 16-bit adc, voltage/current/temperature monitoring and supervision ltc3883 single output polyphase step-down dc/dc controller 0.5% tue 16-bit adc, voltage/current/temperature monitoring and supervision v in swx tg 62 5 57 19 61 run/ss sgnd v fb pgnd dc/dc converter mmbt3906 330nf load v dac2 v sensep2 27 t sense2 v sensem2 v out_en2 46 i sensem2 45 i sensep2 refp refm ltc2974 gnd 20 gnd 21 gnd 37 gnd 39 gnd 2974 ta02 intermediate bus 7 auxfaultb to/from other ltc2974s, ltc2978s and microcontroller 25 faultb0 0.1f 65 28 13 9 18 share_clk 29 sda 30 scl 31 alertb 17 pwrgd 23 22 control3 33 control2 control1 32 control0 24 wdi/resetb gnd wp v dd25 14 v dd25 51 11 12 10 36 35 3.3v nc 52 nc 55 nc 56 nc 59 nc 60 nc 8 dnc v dd33 v dd33 v pwr asel1 asel0 v in_sns 26 faultb1 0.1f 0.1f bg v in swx tg 50 6 58 49 run/ss sgnd v fb pgnd dc/dc converter mmbt3906 330nf load v dac3 v sensep3 34 t sense3 v sensem3 v out_en3 48 i sensem3 47 i sensep3 bg 2 3 53 1 v dac0 v sensep0 15 t sense0 v sensem0 v out_en0 42 38 40 i sensem0 41 i sensep0 64 4 54 63 v dac1 v sensep1 16 t sense1 v sensem1 v out_en1 44 i sensem1 43 i sensep1 10k 5.49k 3.3v 3.3v 10k 10k 10k 10k 10k 10k 10k 10k 10k 10k v in swx tg run/ss sgnd v fb pgnd dc/dc converter bg v in swx tg run/ss sgnd v fb pgnd dc/dc converter bg mmbt3906 330nf load mmbt3906 330nf load 3.3v 0v

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