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1 ltc1643al ltc1643al-1/ltc1643ah 1643afb pci-bus hot swap controller hot swappable pci supply allows safe board insertion and removal from a live pci slot works on either a motherboard (ltc1643ah) or compactpci tm card (ltc1643al/ltc1643al-1) controls 12v, 3.3v, 5v, 12v supplies programmable foldback current limit with circuit breaker user-programmable supply voltage power-up rate high side drive for external n-channel mosfets C12v and 12v on-chip switches fault and power-good outputs available in a narrow 16-lead ssop package the ltc ? 1643a is a hot swap tm controller that allows a board to be safely inserted and removed from a live pci-bus slot. two external n-channel transistors control the 3.3v and 5v supplies while on-chip switches control the C12v and 12v supplies. all supply voltages can be ramped up at a program- mable rate. an electronic circuit breaker protects all four supplies against overcurrent faults. the foldback current limit feature limits current spikes and power dissipation when shorts occur and allows boards with large capacitances to be powered up without tripping the circuit breaker. the pwrgd output indicates when all of the supply voltages are within tolerance and the fault output indicates an overcurrent condition. the on(ltc1643ah)/on (ltc1643al/ ltc1643al-1) pin is used to cycle the board power or reset the circuit breaker. the ltc1643al-1 has the 12v power good comparators disabled. the ltc1643a is available in a 16-pin narrow ssop package. pci-based servers compactpci compliant boards features descriptio u applicatio s u typical applicatio n u r2 0.005 ? q2 irf7413 q1 irf7413 r1 0.007 ? r5 10 ? r6 10 ? r7 100 ? c1 0.047 f 5v 5a 3.3v 7.6a gnd C12v 100ma 12v 500ma r3 10k r4 10k 11 3 13 12 14 16 15 4 10 9 8 1 2 5 6 7 3v in gnd 12v in v eein on fault pwrgd 3v sense 5v sense 3v out ltc1643ah 5v out 12v out v eeout timer 5v in gate 1643a ta01 system power supply pci power system controller c2 0.1 f reset logic reset , lt, ltc and ltm are registered trademarks of linear technology corporation. hot swap is a registered trademark of linear technology corporation. all other trademarks are the property of their respective owners.
2 ltc1643al ltc1643al-1/ltc1643ah 1643afb gn part marking symbol parameter conditions min typ max units i dd v 12vin supply current on = gnd, on = 3v 3.5 8 ma v lko undervoltage lockout 12v in 7 9.5 10.8 v 3v in 2.25 2.5 2.75 v 5v in 2.25 2.5 2.75 v v fb foldback current limit voltage v fb = (v 5vin C v 5vsense ), v 5vout = 0v 4 7.5 12 mv v fb = (v 5vin C v 5vsense ), v 5vout > 4v 40 53 65 mv v fb = (v 3vin C v 3vsense ), v 3vout = 0v 4 7.5 12 mv v fb = (v 3vin C v 3vsense ), v 3vout > 2v 40 53 65 mv t cb circuit breaker trip filter time 14.6 s i cp gate pin output current charge pump on, v gate = gnd, fault = high C 20 C 62 C 100 a charge pump off, v gate = 5v, fault = high 200 a charge pump off, v gate = 2v, fault = low 3 17.5 ma ? v gate external gate voltage (v 12vin C v gate ) 100 200 mv v drop internal switch voltage drop (v 12vin C v 12vout ), 0 c t a 70 c 225 600 i 12vout = 500ma C 40 c t a 85 c 225 750 mv (v eeout C v eein ), i veein = 100ma 125 250 mv i cl current foldback 12v in = 12v, 12v out = 0v 50 250 600 ma 12v in = 12v, 12v out = 10v 525 850 1500 ma v eein = C12v, v eeout = 0v (ltc1643al/ltc1643ah only) 50 160 500 ma v eein = C12v, v eeout = C 10v 225 450 800 ma t ts thermal shutdown temperature 150 c v th power-good threshold voltage v 12vout 0 c t a 70 c 10.8 11.1 11.4 v ltc1643ah/ltc1643al only C 40 c t a 85 c 10.4 11.1 11.4 v v eeout 0 c t a 70 c C 10.2 C 10.5 C 10.8 v ltc1643ah/ltc1643al only C 40 c t a 85 c C 10.0 C 10.5 C 10.8 v absolute m axi m u m ratings w ww u package/order i n for m atio n w u u order part number (note 1) supply voltages 12v in ................................................................ 13.2v v eein .............................................................. C13.2v input voltage (pin 5) ................ C 0.3v to (12v in + 0.3v) output voltages (pins 6, 7) ...... C 0.3v to (12v in + 0.3v) analog voltages (pins 3, 4, 9, 10 to 14) ........ C 0.3v to (12v in + 0.3v) v eeout ............................................ C13.2v to + 0.3v 12v out .............................................. C 0.3v to 13.2v operating temperature range ltc1643alc/ltc1643al-1c/ ltc1643ahc ........................................... 0 c to 70 c ltc1643ali/ltc1643al-1i/ ltc1643ahi ...................................... C 40 c to 85 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c top view gn package 16-lead narrow plastic ssop 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 12v in v eein 3v out timer on/on* fault pwrgd gnd 12v out v eeout 5v out 5v in 5v sense gate 3v sense 3v in *on for ltc1643ah, on for ltc1643al/ltc1643al-1 t jmax = 150 c, ja = 135 c/ w ltc1643ahcgn ltc1643alcgn ltc1643al-1cgn ltc1643ahign ltc1643align ltc1643al-1ign dc electrical characteristics the denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. v 12vin = 12v, v eein = 12v, v 3vin = 3.3v, v 5vin = 5v (note 2) 1643ah 1643al 643al1 643ahi 643ali 43al1i consult ltc marketing for parts specified with wider operating temperature ranges. order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpb lead free part marking: http://www.linear.com/leadfree/
3 ltc1643al ltc1643al-1/ltc1643ah 1643afb dc electrical characteristics typical perfor m a n ce characteristics uw 3.3v and 5v current foldback profile output voltage (v) 0 output current (a) 11 10 9 8 7 6 5 4 3 2 1 0 4 1643a g01 1 2 3 5 r sense = 0.005 ? 3v out 5v out output voltage (v) 0 output current (a) 1.0 0.5 0 C8 C10 1643a g03 C2 C4 C6 C12 output voltage (v) 0 output current (a) 1.0 0.5 0 810 1643a g02 2 4 6 12 12v current foldback profile 12v current foldback profile symbol parameter conditions min typ max units v th power-good threshold voltage v 3vout 0 c t a 70 c 2.8 2.9 3.0 v C40 c t a 85 c 2.75 2.9 3.0 v v 5vout 0 c t a 70 c 4.5 4.65 4.75 v C40 c t a 85 c 4.4 4.65 4.75 v v il input low voltage on/on, fault 0.8 v v ih input high voltage on/on, fault 2v v ol output low voltage fault, pwrgd, i = 3ma 0.4 v i in on/on pin input current on/on = gnd 0.08 10 a on/on= 12v in 0.08 10 a 5v sense input current 5v sense = 5v 50 100 a 3v sense input current 3v sense = 3v 50 100 a 5v in input current 5v in = 5v 460 700 a 3v in input current 3v in = 3v 320 600 a 5v out input current 5v out = 5v, on = 3v, on = gnd 240 500 a 3v out input current 3v out = 3.3v, on = 3v, on = gnd 220 500 a r dis 5v out discharge impedance on = gnd or on = 3v 100 ? 3v out discharge impedance on = gnd or on = 3v 70 ? 12v out discharge impedance on = gnd or on = 3v 450 ? v eeout discharge impedance on = gnd or on = 3v 1600 ? i timer timer pin current timer on, v timer = gnd C15 C22 C27 a timer off, v timer = 5v 45 ma v timer timer threshold voltage (v 12vin C v timer ) 0.5 0.9 1.3 v 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. 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. the denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. v 12vin = 12v, v eein = 12v, v 3vin = 3.3v, v 5vin = 5v (note 2)
4 ltc1643al ltc1643al-1/ltc1643ah 1643afb typical perfor m a n ce characteristics uw temperature ( c) C50 timer current ( a) 100 1643a g04 050 23.5 23.0 22.5 22.0 21.5 21.0 20.5 20.0 19.5 C25 25 75 125 timer current vs temperature temperature ( c) C50 gate i sink (ma) 25.0 22.5 20.0 17.5 15.0 12.5 10.0 25 75 1643a g05 C25 0 50 100 125 fault = low gate i sink vs temperature temperature ( c) C50 gate current ( a) 90 80 70 60 50 40 0 50 75 1643a g06 C25 25 100 125 gate current vs temperature power good threshold voltage vs temperature (12v out ) temperature ( c) C50 power good threshold voltage (v) 11.14 11.12 11.10 11.08 11.06 11.04 0 50 75 1643a g07 C25 25 100 125 power good threshold voltage vs temperature (5v out ) temperature ( c) C50 power good threshold voltage (v) 4.68 4.67 4.66 4.65 4.64 4.63 4.62 25 75 1643a g08 C25 0 50 100 125 temperature ( c) C50 power good threshold voltage (v) 100 1643a g09 050 2.904 2.903 2.902 2.901 2.900 2.899 2.898 2.897 2.896 C25 25 75 125 power good threshold voltage vs temperature (3v out ) power good threshold voltage vs temperature (v eeout ) temperature ( c) C50 power good threshold voltage (v) 100 1643a g10 050 C10.58 C10.56 C10.54 C10.52 C10.50 C10.48 C10.46 C10.44 C10.42 C25 25 75 125 12v internal switch voltage drop vs temperature temperature ( c) 325 300 275 250 225 200 175 150 lt 1643a g11 internal switch voltage drop (mv) C50 25 75 C25 0 50 100 125 i 12vout = 500ma v ee internal switch voltage drop vs temperature temperature ( c) C50 internal switch voltage drop (mv) 180 160 140 120 100 80 60 25 75 1643a g12 C25 0 50 100 125 i veein = 100ma
5 ltc1643al ltc1643al-1/ltc1643ah 1643afb typical perfor m a n ce characteristics uw temperature ( c) C50 circuit breaker trip filter time ( s) 15.50 15.25 15.00 14.75 14.50 14.25 14.00 25 75 1643a g13 C25 0 50 100 125 circuit breaker trip filter time vs temperature timer threshold voltage vs temperature temperature ( c) C50 timer threshold voltage (v) 1.0 0.9 0.8 0.7 25 75 1643a g14 C25 0 50 100 125 v 12vin C v timer 12v in supply current vs temperature temperature ( c) C50 12v in supply current (ma) 3.72 3.70 3.68 3.66 3.64 3.62 0 50 75 1643a g15 C25 25 100 125 v eein supply current vs temperature 5v in supply current vs temperature temperature ( c) C50 v eein supply current (ma) 0.90 0.89 0.88 0.87 0.86 0.85 0.84 25 75 1643a g16 C25 0 50 100 125 temperature ( c) 270 268 266 264 262 260 258 256 lt 1643a g17 5v in supply current ( a) C50 25 75 C25 0 50 100 125 3v in supply current vs temperature temperature ( c) C50 3v in supply current ( a) 275.0 272.5 270.0 267.5 265.0 262.5 260.0 25 75 1643a g18 C25 0 50 100 125 v ol vs temperature temperature ( c) C50 v ol (mv) 350 300 250 200 150 100 50 25 75 1643a g19 C25 0 50 100 125 i = 3ma fault pwrgd temperature ( c) C50 undervoltage lockout (v) 9.515 9.510 9.505 9.500 9.495 9.490 9.485 25 75 1643a g20 C25 0 50 100 125 12v in undervoltage lockout vs temperature temperature ( c) C50 undervoltage lockout (v) 2.454 2.452 2.450 2.448 2.446 2.444 2.442 25 75 1643a g21 C25 0 50 100 125 5v in undervoltage lockout vs temperature
6 ltc1643al ltc1643al-1/ltc1643ah 1643afb typical perfor m a n ce characteristics uw v ee current foldback vs temperature i sink (ma) 0 v ol (mv) 6 10 1643a g27 24 8 800 700 600 500 400 300 200 100 0 fault pwrgd v ol vs i sink (25 c) timer (pin 4): analog current fault inhibit timing input. connect a capacitor from timer to gnd. with the chip turned off (on = gnd or on = high) or the internal circuit breaker tripped (fault = gnd), the timer pin is internally held at gnd. when the chip is turned on, a 22 a pull-up current source is connected to timer. current limit faults will be ignored until the voltage at the timer pin rises to within 0.9v of 12v in . on/on (pin 5): digital input.the ltc1643al/ltc1643al-1 have an active low enable, on, and the ltc1643ah has an active high enable, on. when the on pin is pulled high or pi n fu n ctio n s uuu 12v in (pin 1): 12v supply input. it powers all the chips internal circuitry. a 0.5 ? switch is connected between 12v in and 12v out with a foldback current limit. an under- voltage lockout circuit prevents the switches from turning on while the 12v in pin voltage is less than 9.5v typically. v eein (pin 2): C 12v supply input. a 1.2 ? switch is connected between v eein and v eeout with a foldback current limit. 3v out (pin 3): analog input. used to monitor the 3.3v output supply voltage. the pwrgd signal cannot go low until the 3v out pin exceeds 2.9v typically. temperature ( c) 70 60 50 40 30 20 10 0 1643a g24 foldback current limit voltage (mv) C50 25 75 C25 0 50 100 125 3v out = 3.3v 3v out = 0v 3v in foldback current limit voltage vs temperature temperature ( c) C50 undervoltage lockout (v) 2.454 2.452 2.450 2.448 2.446 2.444 2.442 25 75 1643a g21 C25 0 50 100 125 3v in undervoltage lockout vs temperature temperature ( c) 70 60 50 40 30 20 10 0 1643a g23 foldback current limit voltage (mv) C50 25 75 C25 0 50 100 125 5v out = 5v 5v out = 0v 5v in foldback current limit voltage vs temperature 12v current foldback vs temperature temperature ( c) C50 current foldback (ma) 1200 1000 800 600 400 200 0 25 75 1643a g26 C25 0 50 100 12v out = 12v 12v out = 0v temperature ( c) C50 current foldback (ma) 600 500 400 300 200 100 0 25 75 1643a g25 C25 0 50 100 v eeout = C12v v eeout = 0v
7 ltc1643al ltc1643al-1/ltc1643ah 1643afb 3v sense (pin 10): the 3.3v current limit set pin. with a sense resistor placed in the supply path between 3v in and 3v sense , the gate pin voltage will be adjusted to maintain a constant voltage across the sense resistor and a con- stant current through the switch. a foldback feature makes the current limit decrease as the voltage at the 3v out pin approaches gnd. to disable the current limit, 3v sense and 3v in can be shorted together. gate (pin 11): high side gate drive for the external n-channel pass transistors. requires an external series rc network for the current limit loop compensation and setting the minimum ramp-up rate. during power-up, the slope of the voltage rise at the gate is set by the 62 a current source connected to 12v in and the external ca- pacitor connected to gnd or by the 3.3v or 5v current limit and the bulk capacitance on the 3v out or 5v out suppy lines. during power-down, the slope of the falling voltage is set by the 200 a current source connected to gnd and the external gate capacitor. the voltage at the gate pin will be modulated to maintain a constant current when either the 3v or 5v supplies go into current limit. when a current limit fault occurs after the inhibit period set by the timer pin capacitance, the undervoltage lockout circuit on 3.3v, 5v or 12v trips or the fault pin is pulled low, the gate pin is immediately pulled to gnd. 5v sense (pin 12): 5v current limit set pin. with a sense resistor placed in the supply path between 5v in and 5v sense , the gate pin voltage will be adjusted to maintain a constant voltage across the sense resistor and a con- stant current through the switch. a foldback feature makes the current limit decrease as the voltage at the 5v out pin approaches gnd. to disable the current limit, 5v sense and 5v in can be shorted together. 5v in (pin 13): analog input. used to monitor the 5v input supply voltage. an undervoltage lockout circuit prevents the switches from turning on when the voltage at the 5v in pin is less than 2.5v typically. 5v out (pin 14): analog input. used to monitor the 5v output supply voltage. the pwrgd signal cannot go low until the 5v out pin exceeds 4.65v typically. the on pin pulled low, the gate pin is pulled high by a 62 a current source and the internal 12v and C 12v switches are turned on. when the on pin is pulled low or the on pin pulled high, the gate pin will be pulled to ground by a 200 a current source and the 12v and C 12v switches turned off. the on/on pin is also used to reset the electronic circuit breaker. if the on/on pin is cycled following the trip of the circuit breaker, the circuit breaker is reset and a normal power-up sequence will occur. fault (pin 6): open-drain digital i/o. fault is pulled low when a current limit fault is detected. current limit faults are ignored while the voltage at the timer pin is less than 12v in C 0.9v. once the timer cycle is complete, fault will pull low typically 14.6 s after any of the supplies go into current limit. at the same time, the gate and timer pins are pulled to gnd and the 12v and C12v switches are turned off. the chip will remain latched in the off state until the on/on pin is toggled or the power is cycled. forcing the fault pin low with an external pull-down will immediately turn off the internal switches and force the gate and timer pins to gnd independent of the state of the on/on pin. however, the chip is not latched into the off state, so when the fault pin is released, the state of the chip will be determined by the on pin. pwrgd (pin 7): open-drain digital power-good output. pwrgd remains low while v 12vout 11.4v, v 3vout 3v, v 5vout 4.75v and v eeout C 10.8v. the ltc1643al-1 has the power good comparators connected to the 12v out and v eeout pins disabled, with only the 3v out and 5v out outputs being monitored to generate pwrgd. when one of the supplies falls below its power-good threshold voltage, pwrgd will go high after a 15 s deglitching time. the switches will not be turned off when pwrgd goes high. gnd (pin 8): chip ground. 3v in (pin 9): 3.3v supply sense input. an undervoltage lockout circuit prevents the switches from turning on when the voltage at the 3v in pin is less than 2.5v typically. if no 3.3v input supply is available, tie 3v in to the 5v in pin. pi n fu n ctio n s uuu
8 ltc1643al ltc1643al-1/ltc1643ah 1643afb block diagra m w + C + C + C + C logic 9.5v uvl 5v out + C 3v out 12v in 62 a 200 a q5 on/on fault 22 a 3v sense gate 5v in 5v sense 12v in 12v out v eein v eeout timer gnd 12v in 3v in 5v out 3v out 2.5v uvl 2.5v uvl ref ref ref ltc1643ah/ltc1643al only ltc1643ah/ltc1643al only q2 q8 ref 1643a bd c p3 + C + C + C c p4 c p5 c p7 q3 q4 5 13 1 16 4 2 15 8 12 11 10 9 3 14 6 7 pwrgd q7 q1 q9 q10 q6 applicatio n s i n for m atio n wu u u hot circuit insertion when a circuit board is inserted into a live pci slot, the supply bypass capacitors on the board can draw huge transient currents from the pci power bus as they charge up. the transient currents can cause permanent damage to the connector pins and cause glitches on the power bus, causing other boards in the system to reset. the ltc1643a is designed to turn a boards supply voltages on and off in a controlled manner, allowing the board to be safely inserted or removed from a live pci slot without glitching the system power supplies. the chip also protects the pci supplies from shorts and monitors the supply voltages. the ltc1643ah is designed for motherboard applica- tions, while the ltc1643al/ltc1643al-1 are designed for compactpci applications where the chip resides on the plug-in board. v eeout (pin 15): C12v supply output. a 1.2 ? switch is connected between v eein and v eeout . v eeout must exceed C10.8v before the pwrgd signal can go high on the ltc1643ah and ltc1643al. pi n fu n ctio n s uuu 12v out (pin 16): 12v supply output. a 0.5 ? switch is connected between 12v in and 12v out . 12v out must exceed 11.4v before the pwrgd signal can go high on the ltc1643ah and ltc1643al.
9 ltc1643al ltc1643al-1/ltc1643ah 1643afb ltc1643a feature summary 1. allows safe board insertion and removal from either a motherboard (ltc1643ah) or compactpci board (ltc1643al/ltc1643al-1). 2. controls all four pci supplies: C12v, 12v, 3.3v and 5v. 3. programmable foldback current limit: a programmable analog current limit with a value that depends on the output voltage. if the output is shorted to ground, the current limit drops to keep power dissipation and supply glitches to a minimum. 4. programmable circuit breaker: if a supply remains in current limit too long, the circuit breaker will trip, the supplies will be turned off and the fault pin pulled low. 5. current limit power-up: the supplies are allowed to power up in current limit. allows the chip to power up boards with widely varying capacitive loads without tripping the circuit breaker. the maximum allowable power-up time is programmable using the timer pin. 6. C12v and 12v power switches on chip. 7. power good output: monitors the voltage status of the four supply voltages, except the ltc1643al-1 which only monitors 3v out and 5v out . 8. space saving 16-pin ssop package. pci power requirements pci systems usually require four power rails: 5v, 3.3v, 12v and C12v. systems implementing the 3.3v signaling environment are usually required to provide all four rails in every system. systems implementing the 5v signaling environment may either ship the 3.3v supply with the system or provide a means to add it afterward. the tolerance of the supplies as measured at the components on the plug-in card is summarized in table 1. applicatio n s i n for m atio n wu u u some 12v supplies in compactpci applications are not well regulated and can violate the tolerance specification. for these applications, the ltc1643al-1 should be used because the pwrgd signal does not depend on 12v outputs. power-up sequence the power supplies are controlled by placing external n-channel pass transistors in the 3.3v and 5v power paths, and internal pass transistors for the 12v and C12v power paths (figure 1). resistors r1 and r2 provide current fault detection and r7 and c1 provide current control loop compensation. resistors r5 and r6 prevent high frequency oscillations in q1 and q2. when the on pin (pin 5) is pulled high, the pass transistors are allowed to turn on and a 22 a current source is connected to the timer pin (pin 4) (figure 2). the current in each pass transistor increases until it reaches the current limit for each supply. each supply is then allowed to power up at the rate dv/dt = 62 a/c1 or as determined by the current limit and the load capacitance whichever is slower. current limit faults are ignored while the timer pin (pin 4) voltage is ramping up and is less than 0.9v below 12v in (pin 1). once all four supply voltages are within tolerance, the pwrgd pin (pin 7) will pull low. power-down sequence when the on pin (pin 5) is pulled low, a power-down sequence begins (figure 3). internal switches are connected to each of the output supply voltage pins to discharge the bypass capacitors to ground. the timer pin (pin 4) is immediately pulled low. the gate pin (pin 11) is pulled down by a 200 a current source to prevent the load currents on the 3.3v and 5v supplies from going to zero instantaneously and glitching the power supply voltages. when any of the output voltages dip below its threshold, the pwrgd pin (pin 7) pulls high. table 1. pci power supply requirements capacitive supply tolerance load 5v 5v 5% < 3000 f 3.3v 3.3v 0.3v < 3000 f 12v 12v 5% < 500 f C 12v C12v 10% < 120 f
10 ltc1643al ltc1643al-1/ltc1643ah 1643afb figure 2. normal power-up sequence figure 3. normal power-down sequence on 10v/div timer 10v/div gate 10v/div 12v out 5v/div 5v out 5v/div 3v out 5v/div v eeout 5v/div fault 10v/div pwrgd 10v/div 10ms/div 1643a f02 on 10v/div timer 10v/div gate 10v/div 12v out 5v/div 5v out 5v/div 3v out 5v/div v eeout 5v/div fault 10v/div pwrgd 10v/div 10ms/div 1643a f03 r2 0.005 ? q2 irf7413 q1 irf7413 r1 0.007 ? r5 10 ? r6 10 ? r7 100 ? c1 0.047 f 5v 5a 3.3v 7.6a gnd C12v 100ma 12v 500ma r3 10k r4 10k 11 3 13 12 14 16 15 4 10 9 8 1 2 5 6 7 3v in gnd 12v in v eein on fault pwrgd 3v sense 5v sense 3v out ltc1643ah 5v out 12v out v eeout timer 5v in gate 1643a f01 system power supply pci power system controller c2 0.1 f reset logic reset 4 3 2 1 4 3 2 1 figure 1. typical pci application applicatio n s i n for m atio n wu u u
11 ltc1643al ltc1643al-1/ltc1643ah 1643afb applicatio n s i n for m atio n wu u u timer during a power-up sequence, a 22 a current source is connected to the timer pin (pin 4) and current limit faults are ignored until the voltage ramps to within 0.9v of 12v in (pin 1). this feature allows the chip to power up a pci slot that can accept boards with widely varying capacitive loads on the supplies. the power-up time will be: t cv ii on supply supply limit load ? ? 2 ? for c supply = 2000 f, v supply = 5v, i limit = 7a, i load = 5a, the turn-on time will be ~10ms. the timer period should be set longer than the maximum supply turn-on time but short enough to not exceed the maximum safe operating area of the pass transistor during a short circuit. the timer period will be: t c v a timer timer = ?. 11 1 22 for c timer = 0.1 f, the timer period will be ~ 50ms. the timer pin (pin 4) is immediately pulled low when on (pin 5) goes low. thermal shutdown the internal switches for the 12v and C12v supplies are protected by an internal current limit and thermal shut- down circuit. when the temperature of chip reaches 150 c, all switches will be latched off and the fault pin (pin 6) will be pulled low. short-circuit protection during a normal power-up sequence, if the timer (pin 4) is done ramping and a supply is still in current limit, all of the pass transistors will be immediately turned off and the fault pin (pin 6) will be pulled low as shown in figure 4. if a short circuit occurs after the supplies are powered up, the shorted supplys current will drop immediately to the limit value (figure 5). if the supply remains in current limit for more than 14.6 s, all of the supplies will be latched off. the 14.6 s delay prevents quick current spikesfor example, from a fan turning onfrom causing false trips of the circuit breaker. the chip will stay in the latched-off state until on pin (pin 5) is cycled low then high, or the 12v in pin (pin 1) power supply is cycled. to prevent excessive power dissipation in the pass tran- sistors and to prevent voltage spikes on the supplies during short-circuit conditions, the current limit on each supply is designed to be a function of the output voltage. as the output voltage drops, the current limit decreases. unlike a traditional circuit breaker function where huge currents can flow before the breaker trips, the current foldback feature assures that the supply current will be kept at a safe level and prevent voltage glitches when powering up into a short. the current limit for the 5v and 3.3v supplies is set by placing a sense resistor between 5v in (pin 13) and 5v sense (pin 12) and between 3v in (pin 9) and 3v sense (pin 10). the current limit will be set by: i limit = 53mv/r sense for a 0.005 ? resistor, the current limit will be set at 10.6a and fold back to 1.5a when the output is shorted. for a 0.007 ? resistor, the current limit will be set at 7.6a and fold back to 1.1a when the output is shorted. the current limit for the internal 12v switch is set at 850ma folding back to 250ma and the C12v switch at 450ma folding back to 160ma. in systems where it is possible to exceed the current limit for a short amount of time, it might be necessary to prevent the analog current loop from responding quickly so the output voltage does not droop. this can be accom- plished by adding an rc filter across the sense resistor as shown in figure 6. r4 should be 20 ? or less to prevent offset errors. a 0.1 f capacitor gives a delay of about 1.5 s and a 1 f capacitor gives a delay of about 15 s. compactpci application the ltc1643al is designed for hot swapping compactpci boards. the typical application is shown in figure 7. the 3.3v, 5v, 12v and C12v inputs to the ltc1643al come from the medium length power pins. the long 3.3v, 5v and v(i/o) pins power up the pull-up resistors, bus precharge
12 ltc1643al ltc1643al-1/ltc1643ah 1643afb figure 6. delay in the current limit loop r2 0.005 ? q2 irf7413 q1 irf7413 r1 0.007 ? r5 10 ? r3 20 ? r6 10 ? r4 20 ? r7 100 ? c1 0.047 f 5v 5a 5v 3.3v 3.3v 7.6a 11 3 13 12 14 10 9 3v in 3v sense 5v sense 3v out ltc1643al 5v out 5v in gate 1643a f06 c2 1 f c3 1 f 4 3 2 1 4 3 2 1 applicatio n s i n for m atio n wu u u figure 4. power-up into a short on 3.3v output figure 5. short circuit on 5v followed by circuit breaker reset on 10v/div timer 10v/div gate 10v/div 12v out 5v/div 3v out 5v/div 5v out 5v/div v eeout 5v/div fault 10v/div pwrgd 10v/div 20ms/div 1643a f04 on 10v/div timer 10v/div gate 10v/div 12v out 5v/div 5v out 5v/div 3v out 5v/div v eeout 5v/div fault 10v/div pwrgd 10v/div 20ms/div 1643a f05
13 ltc1643al ltc1643al-1/ltc1643ah 1643afb applicatio n s i n for m atio n wu u u circuit, pci bridge chip and the local_pci_reset# logic circuitry. the bd_sel# signal is connected to the on pin while the pwrgd pin is connected to the healthy# signal. the heathly# signal is combined with the pci_reset# signal to generate the local_pci_reset# signal. capacitors c6 and c7 provide chip bypassing on the 12v and C12v inputs. diode d2 protects the part from voltage surges below C13.2v on the C12v supply. the 1v precharge voltage for the data bus lines is gener- ated by an lt1117 low dropout regulator. the output of the lt1117 is set to 1.8v, then the voltage is dropped by a 1n4148 diode to generate 1v. the precharge circuit is capable of sourcing and sinking 40ma. r1 0.005 ? 1% v(i/o) v(i/o) v(i/o) v(i/o) q2 irf7413 q1 irf7413 r2 0.007 ? 1% r3 10 ? 5% r4 10 ? 5% r5 100 ? 5% c1 0.047 f 5v 5a med 5v med 3.3v bd_sel# long gnd pci_rst# i/o 3.3v 7.6a C12v 100ma 12v 500ma precharge out 1v 20% i out = 40ma r9 2k 5% r12 3 ? 5% r10 2k 5% r8 1.2k 5% local_pci_reset# data line example data bus r14 10 ? , 5% 11 3 13 12 14 16 15 4 8 10 9 5 6 3v in 1 2 12v C12v 12v in v eein on fault 3v sense 5v sense 3v out ltc1643al 5v out 12v out v eeout timer 5v in gate healthy# 7 pwrgd 1643a f07 c2 0.1 f gnd compactpci connector c6 0.1 f c5 0.1 f c3 0.01 f c4 1 f d1 1n4148 r13 10k 5% reset# long 3.3v long 3.3v long 5v 3.3v pci bridge (21154) 5v out in adj lt1117 r11 24 ? 5% r6 130 ? 1% r7 56.2 ? 1% i/o r13 2k 5% r11 10 ? ? 5% d2* 12v d3* 12v * bzx84c15 (sot-23) ? value may vary for backplanes without bypass capacitance 4 3 2 1 4 3 2 1 figure 7. typical compactpci application ltc1643al-1 the ltc1643al-1 is designed for compactpci designs where the 12v supplies are not being used on the board or the supplies are not well regulated. the power good comparators on the 12v out and v eeout pins are disabled. the v eein pin can be connected to gnd and the part will still operate normally if a C 12v out output is not needed. however, 12v is still required at the 12v in pin for the part to function. refer to figure 10 for a typical ltc1643al-1 application circuit.
14 ltc1643al ltc1643al-1/ltc1643ah 1643afb r2 0.005 ? q2 irf7413 q1 irf7413 r1 0.007 ? r5 10 ? r6 10 ? r8 100k r7 100 ? c1 0.047 f 5v 5a 12v 1.5a 3.3v 7.6a gnd r3 10k r4 10k 11 3 13 12 16 15 4 10 9 8 1 2 5 6 7 3v in gnd on fault note: intended for pci applications only pwrgd 3v sense 5v sense 3v out ltc1643ah 12v out v eeout timer 5v in gate 1643a f08 system power supply pci power system controller c2 0.1 f c3 0.1 f r10 200 ? r9 200 ? q5 tp0610t q6 si9410dy q4 si9400 q3 tp0610t d1 1n4148 12v in v eein C12v 1.5a 4 3 2 1 4 3 2 1 10 ? figure 8. increasing 12v and 12v current capability for pci applications applicatio n s i n for m atio n wu u u increasing 12v and 12v current capability for pci applications the internal switches of the ltc1643a are designed for up to 500ma loads on 12v and 200ma on C12v. if more current is needed, then the circuits in figure 8 can be used. for the 12v supply, p-channel transistor q4 is placed in parallel with the internal switch. when the ltc1643ah is turned off, the gate pin is held low and transistor q3 is turned on which pulls the gate of q4 high, turning it off. when the ltc1643ah is turned on, the gate pin goes high, turning off q3 and allowing r8 to pull the gate of q4 low to turn it on. because q4 is in parallel with the internal 12v switch, the load current will be shared in proportion to their respective r ds(on) values. for example, if the r ds(on) of the external switch is 0.2 ? and the internal switch is 0.4 ? , then, at 1.5a load current, the external switch will provide 1a and the internal switch 500ma. the circuit breaker current will be reached when the internal current reaches 1a and the external current is 2a or 3a load current. for the C12v supply, n-channel transistor q6 is used to provide the extra load current. when the ltc1643ah is turned on, the internal v ee switch is turned on and the C12v output starts to pull down through d1 and turns on q5. when q5 turns on, the gate of q6 starts to rise, turning it on. when the ltc1643ah turns off, the v eeout pin is pulled up to ground, diode d1 is reversed biased, and transistor q5 turns off, which allows resistor r10 to turn off q6. the internal C12v switch provides the current limit for the supply, but because the high r ds(on) of the internal switch (1.2 ? ) is in series with d1, very large currents can flow through q6 before the circuit breaker trips. however, if a short to ground occurs on the C12v output, diode d1 will prevent q5 from turning on, which will prevent q6 from turning on.
15 ltc1643al ltc1643al-1/ltc1643ah 1643afb package descriptio n u 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. figure 9. system without 3.3v supply typical applicatio n s u q1 irf7413 r1 0.007 ? r6 10 ? r7 100 ? c1 0.047 f 5v 5a gnd C12v 100ma 12v 500ma r3 10k r4 10k 11 13 12 14 3 16 15 4 10 9 8 1 2 5 6 7 3v in gnd 12v in v eein on fault pwrgd 3v sense 5v sense 3v out ltc1643ah 5v out 12v out v eeout timer 5v in gate 1643a g09 system power supply pci power system controller c2 0.1 f 4 3 2 1 gn package 16-lead plastic ssop (narrow .150 inch) (reference ltc dwg # 05-08-1641) gn16 (ssop) 0502 12 3 4 5 6 7 8 .229 C .244 (5.817 C 6.198) .150 C .157** (3.810 C 3.988) 16 15 14 13 .189 C .196* (4.801 C 4.978) 12 11 10 9 .016 C .050 (0.406 C 1.270) .015 .004 (0.38 0.10) 45 0 C 8 typ .007 C .0098 (0.178 C 0.249) .053 C .068 (1.351 C 1.727) .008 C .012 (0.203 C 0.305) .004 C .0098 (0.102 C 0.249) .0250 (0.635) bsc .009 (0.229) ref .254 min recommended solder pad layout .150 C .165 .0250 typ .0165 .0015 .045 .005 *dimension does not include mold flash. mold flash shall not exceed 0.006" (0.152mm) per side **dimension does not include interlead flash. interlead flash shall not exceed 0.010" (0.254mm) per side inches (millimeters) note: 1. controlling dimension: inches 2. dimensions are in 3. drawing not to scale
16 ltc1643al ltc1643al-1/ltc1643ah 1643afb lt/lwi 1006 rev b ? printed in usa ? linear technology corporation 2002 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com related parts part number description comments ltc1421 hot swap controller multiple supplies from 3v to 12v and C12v ltc1422 hot swap controller in so-8 single supply form 3v to 12v, reset output lt ? 1640a C 48v hot swap controller in so-8 C10v to C 80v supplies lt1641-1/lt1641-2 positive high voltage hot swap controller in so-8 operates from 9v to 80v, active current limiting ltc1642 fault protected hot swap controller operation up to 15v, handles surges to 33v ltc1644 compactpci hot swap controller 3.3v, 5v, 12v, local reset logic, 1v precharge ltc1645 2-channel hot swap controller operates from 1.2v to 12v, power sequencing ltc1646 dual compactpci hot swap controller 3.3v, 5v supplies, 1v precharge, local reset logic ltc1647 dual hot swap controller dual on pins for supplies from 3v to 15v ltc4211 hot swap controller with multifunction current control 2.5v to 16.5v operation, msop ltc4230 triple hot swap controller 1.7v to 16.5v operation, multifunction current control lt4250 C 48v hot swap controller in so-8 C 20v to C80v supplies, active current limiting ltc4251 C 48v hot swap controller in sot-23 C15v minimum floating supply, active current limiting ltc4252 C 48v hot swap controller in msop floating supply, power good, active current limiting figure 10. compactpci application without 12v outputs typical applicatio n s u r1 0.005 ? 1% v(i/o) v(i/o) v(i/o) q2 irf7413 q1 irf7413 r2 0.007 ? 1% r3 10 ? 5% r4 10 ? 5% r5 100 ? 5% c1 0.047 f 5v 5a med 5v med 3.3v bd_sel# long gnd pci_rst# i/o 3.3v 7.6a precharge out 1v 20% i out = 40ma r9 2k 5% r12 2k 5% local_pci_reset# data line example data bus r10 2k 5% r11 1 ? ? 5% * bzx84c15 (sot-23) ? value may vary for backplanes without bypass capacitance r14 10 ? , 5% 11 3 13 12 14 16 15 4 8 10 9 5 6 3v in 1 2 12v 12v in v eein on fault 3v sense 5v sense 3v out ltc1643al-1 5v out 12v out v eeout nc nc timer 5v in gate healthy# 7 pwrgd 1643a f10 c2 0.1 f gnd compactpci connector c7 0.1 f c3 0.01 f c4 1 f d1 1n4148 r8 1.2k 5% r13 10k 5% reset# long 3.3v long 3.3v long 5v 3.3v pci bridge (21154) 5v out in adj lt1117 r15 24 ? 5% r6 130 ? 1% r7 56.2 ? 1% i/o 4 3 2 1 4 3 2 1 d2* 12v

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