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an important notice at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. production data. LMR33630 snvsan3a ? august 2017 ? revised february 2018 LMR33630 simple switcher ? 3.8-v to 36-v, 3-a synchronous step-down voltage converter 1 1 features 1 ? configured for rugged industrial applications ? input voltage range: 3.8 v to 36 v ? output voltage range: 1 v to 24 v ? output current: 3 a ? peak-current-mode control ? short minimum on-time of 70 ns ? frequency: 400 khz, 1.4 mhz, 2.1 mhz ? junction temperature range ? 40 c to +125 c ? integration simplifies design and reduces size ? integrated synchronous rectification ? integrated compensation network ? best-in-class power dissipation ? > 91% efficiency at full load ? low shutdown quiescent current of 5 a ? low operating quiescent current of 24 a ? flexible system interface ? power-good flag and precision enable ? create a custom design using the LMR33630 with the webench ? power designer 2 applications ? motor drive systems: drones, ac inverters, vf drives, servos ? factory and building automation systems: plc cpu, hvac control, elevator control ? general purpose wide v in power supplies 3 description the LMR33630 simple switcher ? regulator is an easy-to-use, synchronous, step-down dc/dc converter that delivers best-in-class efficiency for rugged industrial applications. the LMR33630 is capable of driving up to 3 a of load current from an input of up to 36 v. the LMR33630 provides high light load efficiency and output accuracy in a very small solution size. features such as a power-good flag and precision enable provide both flexible and easy-to-use solutions for a wide range of applications. the LMR33630 automatically folds back frequency at light load to improve efficiency. integration eliminates most external components and provides a pinout designed for simple pcb layout. protection features include thermal shutdown, input undervoltage lockout, cycle-by-cycle current limit, and hiccup short-circuit protection. the LMR33630 is available in an 8-pin hsoic package. device information (1) part number package body size (nom) LMR33630 hsoic (8) 5.00 mm 4.00 mm (1) for all available packages, see the orderable addendum at the end of the data sheet. space space space space space space space simplified schematic efficiency vs output current v out = 5 v, 400 khz, hsoic 55 60 65 70 75 80 85 90 95 100 0.01 0.1 1 10 efficiency (%) output current (a) 8v 12v 24v 36v c018 v in vin en boot sw fb agnd v out c boot l1 c in c out r fbt r fbb vcc pg pgnd c vcc tools & software technical documents ordernow productfolder support &community
2 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated table of contents 1 features .................................................................. 1 2 applications ........................................................... 1 3 description ............................................................. 1 4 revision history ..................................................... 2 5 device comparison table ..................................... 3 6 pin configuration and functions ......................... 3 7 specifications ......................................................... 4 7.1 absolute maximum ratings ...................................... 4 7.2 esd ratings .............................................................. 4 7.3 recommended operating conditions ...................... 4 7.4 thermal information .................................................. 5 7.5 electrical characteristics ........................................... 5 7.6 timing characteristics ............................................... 6 7.7 system characteristics ............................................. 7 7.8 typical characteristics .............................................. 8 8 detailed description .............................................. 9 8.1 overview ................................................................... 9 8.2 functional block diagram ......................................... 9 8.3 feature description ................................................... 9 8.4 device functional modes ........................................ 14 9 application and implementation ........................ 17 9.1 application information ............................................ 17 9.2 typical application .................................................. 17 9.3 do ' s and don ' ts ....................................................... 27 10 power supply recommendations ..................... 28 11 layout ................................................................... 29 11.1 layout guidelines ................................................. 29 11.2 layout example .................................................... 31 12 device and documentation support ................. 32 12.1 device support .................................................... 32 12.2 documentation support ........................................ 32 12.3 receiving notification of documentation updates 32 12.4 community resources .......................................... 32 12.5 trademarks ........................................................... 33 12.6 electrostatic discharge caution ............................ 33 12.7 glossary ................................................................ 33 13 mechanical, packaging, and orderable information ........................................................... 33 4 revision history changes from original (august 2017) to revision a page ? first release of production-data data sheet ........................................................................................................................... 1
3 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 5 device comparison table part number package frequency rated current body size (nom) LMR33630addar dda (8-pin hsoic) 400 khz 3 a 5.00 mm 4.00 mm LMR33630bddar 1400 khz 3 a LMR33630cddar 2100 khz 3 a 6 pin configuration and functions dda package 8-pin hsoic with powerpad ? top view pin functions for 8-pin dda (hsoic) package pin type description no. name 1 pgnd g power ground terminal. connect to system ground and agnd. connect to c in with short wide traces. 2 vin p input supply to regulator. connect a high-quality bypass capacitor(s) directly to this pin and pgnd. 3 en a enable input to regulator. high = on, low = off. can be connected directly to vin; do not float. 4 pg a open drain power good flag output. connect to suitable voltage supply through a current limiting resistor. high = power ok, low = power bad. flag pulls low when en = low. can be open or grounded when not used. 5 fb a feedback input to regulator. connect to tap point of feedback voltage divider. do not float. do not ground. 6 vcc p internal 5-v ldo output. used as supply to internal control circuits. do not connect to external loads. can be used as logic supply for power-good flag. connect a high-quality, 1- f capacitor from this pin to gnd. 7 boot p boot-strap supply voltage for internal high-side driver. connect a high-quality, 100-nf capacitor from this pin to the sw pin. 8 sw p regulator switch node. connect to power inductor. 9 thermal pad (agnd) g analog ground for regulator and system. ground reference for internal references and logic. all electrical parameters are measured with respect to this pin. connect to system ground on pcb. a = analog, p = power, g = ground 1 2 3 (9) 8 pgnd vin en vcc sw fb pg (agnd) 5 boot 4 6 7 thermal pad
4 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated (1) stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions . exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. (2) the voltage on this pin must not exceed the voltage on the vin pin by more than 0.3 v (3) under some operating conditions the vcc ldo voltage may increase beyond 5.5v. (4) positive current flows into this pin. the maximum current through the mosfet connected to this pin is internally limited. (5) operating at junction temperatures greater than 125 c, although possible, degrades the lifetime of the device. 7 specifications 7.1 absolute maximum ratings over the recommended operating junction temperature range (1) parameter min max unit voltages vin to pgnd ? 0.3 38 v en to agnd (2) ? 0.3 v in + 0.3 fb to agnd ? 0.3 5.5 pg to agnd (2) 0 22 agnd to pgnd ? 0.3 0.3 sw to pgnd ? 0.3 v in + 0.3 v sw to pgnd less than 100-ns transients ? 3.5 38 boot to sw ? 0.3 5.5 vcc to agnd (3) ? 0.3 5.5 current pg to agnd (4) 0 5 ma t j junction temperature (5) ? 40 150 c t stg storage temperature ? 65 150 c (1) jedec document jep155 states that 500-v hbm allows safe manufacturing with a standard esd control process. (2) jedec document jep157 states that 250-v cdm allows safe manufacturing with a standard esd control process. 7.2 esd ratings value unit v (esd) electrostatic discharge human-body model (hbm) (1) 1000 v charged-device model (cdm) (2) 500 (1) recommended operating conditions indicate conditions for which the device is intended to be functional, but do not ensure specific performance limits. for ensured specifications, see electrical characteristics . (2) the voltage on this pin must not exceed the voltage on the vin pin by more than 0.3 v. (3) under no conditions should the output voltage be allowed to fall below zero volts. (4) operating at junction temperatures greater than 125 , although possible, degrades the lifetime of the device. 7.3 recommended operating conditions over the recommended operating junction temperature range of ? 40 c to 125 c (unless otherwise noted) (1) min max unit input voltage vin to pgnd 3.8 36 v en (2) 0 v in pg (2) 0 12 output voltage v out (3) 1 24 v output current i out 0 3 a temperature operating junction temperature, t j (4) ? 40 125 c
5 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated (1) for more information about traditional and new thermal metrics, see the semiconductor and ic package thermal metrics application report. (2) the value of r ja given in this table is only valid for comparison with other packages and can not be used for design purposes. these values were calculated in accordance with jesd 51-7, and simulated on a 4-layer jedec board. they do not represent the performance obtained in an actual application. for design information please see the maximum ambient temperature section. 7.4 thermal information thermal metric (1) (2) LMR33630 unit dda (hsoic) 8 pins r ja junction-to-ambient thermal resistance 42.9 c/w r jc(top) junction-to-case (top) thermal resistance 54 c/w r jb junction-to-board thermal resistance 13.6 c/w jt junction-to-top characterization parameter 4.3 c/w jb junction-to-board characterization parameter 13.8 c/w r jc(bot) junction-to-case (bottom) thermal resistance 4.3 c/w (1) min and max limits are 100% production tested at 25 o c. limits over the operating temperature range verified through correlation using statistical quality control (sqc) methods. limits are used to calculate average outgoing quality level (aoql). (2) this is the current used by the device open loop. it does not represent the total input current of the system when in regulation. (3) when the voltage across the c boot capacitor falls below this voltage, the low side mosfet is turned on to recharge c boot . 7.5 electrical characteristics limits apply over the recommended operating junction temperature (t j ) range of ? 40 c to +125 c, unless otherwise stated. minimum and maximum limits are specified through test, design or statistical correlation. typical values represent the most likely parametric norm at t j = 25 c, and are provided for reference purposes only. unless otherwise stated, the following conditions apply: v in = v en = 12 v. parameter test conditions min (1) typ max (1) unit supply voltage v in minimum operating input voltage 3.8 v i q non-switching input current; measured at vin pin (2) v fb = 1.2 v 24 34 a i sd shutdown quiescent current; measured at vin pin en = 0 5 10 a enable v en-vcc-h en input level required to turn on internal ldo rising threshold 1 v v en-vcc-l en input level required to turn off internal ldo falling threshold 0.3 v v en-h en input level required to start switching rising threshold 1.2 1.231 1.26 v v en-hys hysteresis below v en-h hysteresis below v en-h ; falling 100 mv i lkg-en enable input leakage current v en = 3.3 v 0.2 na internal supplies vcc internal ldo output voltage appearing at the vcc pin 6 v v in 36 v 4.75 5 5.25 v v boot-uvlo bootstrap voltage undervoltage lock-out threshold (3) 2.2 v voltage reference (fb pin) v fb feedback voltage 0.985 1 1.015 v i lkg-fb leakage current into fb pin fb = 1 v 0.2 50 na
6 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated electrical characteristics (continued) limits apply over the recommended operating junction temperature (t j ) range of ? 40 c to +125 c, unless otherwise stated. minimum and maximum limits are specified through test, design or statistical correlation. typical values represent the most likely parametric norm at t j = 25 c, and are provided for reference purposes only. unless otherwise stated, the following conditions apply: v in = v en = 12 v. parameter test conditions min (1) typ max (1) unit (4) the current limit values in this table are tested, open loop, in production. they may differ from those found in a closed loop application. (5) see power-good flag output for details. current limits (4) i sc high-side current limit LMR33630 3.85 4.5 5.05 a i limit low-side current limit LMR33630 2.9 3.5 4.1 a i peak-min minimum peak inductor current LMR33630 0.8 a i zc zero current detector threshold 0.01 a soft start t ss internal soft-start time 2.9 4 6 ms power good (pg pin) v pg-high-up power-good upper threshold - rising % of fb voltage 105% 107% 110% v pg-high-dn power-good upper threshold - falling % of fb voltage 103% 105% 108% v pg-low-up power-good lower threshold - rising % of fb voltage 92% 94% 97% v pg-low-dn power-good lower threshold - falling % of fb voltage 90% 92% 95% t pg power-good glitch filter delay (5) 60 170 s r pg power-good flag r dson v in = v en = 12 v 76 150 ? v en = 0 v 35 60 v in-pg minimum input voltage for proper pg function 50- a, en = 0 v 2 v v pg pg logic low output 50- a, en = 0 v, v in = 2v 0.2 v oscillator ? sw switching frequency "a" version 340 400 460 khz ? sw switching frequency "b" version 1.2 1.4 1.6 mhz ? sw switching frequency "c" version 1.8 2.1 2.4 mhz mosfets r ds-on-hs high-side mosfet on- resistance dda package 95 160 m r ds-on-ls low-side mosfet on- resistance dda package 66 110 m 7.6 timing characteristics limits apply over the recommended operating junction temperature (t j ) range of ? 40 c to +125 c, unless otherwise stated. minimum and maximum limits are specified through test, design or statistical correlation. typical values represent the most likely parametric norm at t j = 25 c, and are provided for reference purposes only. unless otherwise stated, the following conditions apply: v in = v en = 12 v. min nom max unit t on-min minimum switch on-time dda package 75 108 ns t off-min minimum switch off-time dda package 50 85 ns t on-max maximum switch on-time 7 9 s
7 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated (1) deviation is with respect to v in =12 v, i out = 1 a. (2) in dropout the switching frequency drops to increase the effective duty cycle. the lowest frequency is clamped at approximately: ? min = 1 / (t on-max + t off-min ). d max = t on-max /(t on-max + t off-min ). 7.7 system characteristics the following specifications apply only to the typical applications circuit shown in figure 34 , with nominal component values. specifications in the typical (typ) column apply to t j = 25 c only. specifications in the minimum (min) and maximum (max) columns apply to the case of typical components over the temperature range of t j = ? 40 c to 125 c. these specifications are not ensured by production testing. parameter test conditions min typ max unit v in operating input voltage range v out = 3.3 v, i out = 0 a 3.8 36 v v out output voltage regulation for v out = 5 v (1) v out = 5 v, v in = 7 v to 36 v, i out = 0 a to 3 a ? 1.5% 2.5% v out = 5 v, v in = 7 v to 36 v, i out = 1 a to 3 a ? 1.5% 1.5% output voltage regulation for v out = 3.3 v (1) v out = 3.3 v, v in = 3.8 v to 36 v, i out = 0 a to 3 a ? 1.5% 2.5% v out = 3.3 v, v in = 3.8 v to 36 v, i out = 1 a to 3 a ? 1.5% 1.5% i supply input supply current when in regulation v in = 12 v, v out = 3.3 v, i out = 0 a, r fbt = 1 m 25 a v drop dropout voltage; (v in ? v out ) v out = 5 v, i out = 1a dropout at ? 1% of regulation, ? sw = 140 khz 150 mv d max maximum switch duty cycle (2) v in = v out = 12 v, i out = 1 a 98% v hc fb pin voltage required to trip short- circuit hiccup mode 0.4 v t hc time between current-limit hiccup burst 94 ms t d switch voltage dead time 2 ns t sd thermal shutdown temperature shutdown temperature 165 c recovery temperature 148 c
8 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 7.8 typical characteristics unless otherwise specified the following conditions apply: t a = 25 c. v in = 12 v v fb = 1.2 v figure 1. non-switching input supply current en = 0 v figure 2. shutdown supply current v out = 0 v ? s = 400 khz see figure 40 figure 3. short-circuit output current figure 4. precision enable thresholds i out = 1 ma see figure 40 figure 5. uvlo thresholds i out = 0 a v out = 5 v see figure 40 ? sw = 400 khz figure 6. i peak-min 20 22 24 26 28 30 32 34 36 0 5 10 15 20 25 30 35 40 quiescent current (a) input voltage (v) -40c 25c 125c c005 0 1 2 3 4 5 6 7 8 9 10 11 12 0 5 10 15 20 25 30 35 40 shutdown current (a) input voltage (v) -40c 25c 125c c003 500 600 700 800 900 1000 0 5 10 15 20 25 30 35 40 short circuit output current (ma) input voltage (v) -40c 25c 125c c004 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 40 20 0 20 40 60 80 100 120 140 en threshold voltage (v) temperature (c) up dn c006 400 500 600 700 800 900 1,000 1,100 1,200 5 10 15 20 25 30 35 40 peak inductor current (ma) input voltage (v) -40c 25c 125c c006 up dn input voltage (1v/div) output voltage (0.8v/div) 0
9 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 8 detailed description 8.1 overview the LMR33630 is a synchronous peak-current-mode buck regulator designed for a wide variety of industrial applications. the regulator automatically switches modes between pfm and pwm depending on load. at heavy load, the device operates in pwm at a constant switching frequency. at light loads the mode changes to pfm, with diode emulation allowing dcm. this reduces the input supply current and keeps efficiency high. the device features internal loop compensation which reduces design time and requires fewer external components than externally compensated regulators. 8.2 functional block diagram 8.3 feature description 8.3.1 power-good flag output the power-good flag function (pg output pin) of the LMR33630 can be used to reset a system microprocessor whenever the output voltage is out of regulation. this open-drain output goes low under fault conditions, such as current limit and thermal shutdown, as well as during normal start-up. a glitch filter prevents false flag operation for short excursions of the output voltage, such as during line and load transients. the timing parameters of the glitch filter are found in the electrical characteristics table. output voltage excursions lasting less than t pg do not trip the power-good flag. power-good operation can best be understood by reference to figure 7 and figure 8 . note that during initial power-up a delay of about 4 ms (typical) is inserted from the time that en is asserted to the time that the power-good flag goes high. this delay only occurs during start-up and is not encountered during normal operation of the power-good function. + - + - control logic driver hs current sense ls current sense oscillator pwm comp. error amplifier power good control sw vin pgnd fb en int. reg. bias vcc boot agnd 1.0v reference enable logic pg pfm mode control copyright ? 2017, texas instruments incorporated
10 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated feature description (continued) the power-good output consists of an open drain nmos; requiring an external pull up resistor to a suitable logic supply. it can also be pulled up to either vcc or v out , through an appropriate resistor, as desired. if this function is not needed, the pg pin should be grounded. when en is pulled low, the flag output is also forced low. with en low, power good remains valid as long as the input voltage is 2 v (typical). limit the current into the power- good flag pin to 4 ma d.c. the maximum current is internally limited to about 35 ma when the device is enabled and about 65 ma when the device is disabled. the internal current limit protects the device from any transient currents that may occur when discharging a filter capacitor connected to this output. figure 7. static power-good operation high = power good v out pg low = fault (95%) (93%) (107%) (105%) v pg-high_up v pg-high-dn v pg-low-up v pg-low-dn
11 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated feature description (continued) figure 8. power-good-timing behavior 8.3.2 enable and start-up start-up and shutdown are controlled by the en input. this input features precision thresholds, allowing the use of an external voltage divider to provide an adjustable input uvlo (see the external uvlo section). applying a voltage of v en-vcc_h causes the device to enter standby mode, powering the internal vcc, but not producing an output voltage. increasing the en voltage to v en-h fully enables the device, allowing it to enter start-up mode and beginning the soft-start period. when the en input is brought below v en-h by v en-hys , the regulator stops running and enters standby mode. further decrease in the en voltage to below v en-vcc-l completely shuts down the device. this behavior is shown in figure 9 . the en input may be connected directly to vin if this feature is not needed. this input must not be allowed to float. the values for the various en thresholds can be found in the electrical characteristics table. the LMR33630 utilizes a reference-based soft start that prevents output voltage overshoots and large inrush currents as the regulator is starting up. a typical start-up waveform is shown in figure 10 along with typical timings. the rise time of the output voltage is about 4 ms (see electrical characteristics ). (95%) v out (93%) pg t pg glitches do not cause false operation nor reset timer v pg-low-up v pg-low-dn t pg t pg 12 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated feature description (continued) figure 9. precision enable behavior en v cc 0 v en-h v en-h v en-hys v en-vcc-l 5 v v out v out 0 v en-vcc-h
13 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated feature description (continued) figure 10. typical start-up behavior v in = 12 v, v out = 5 v, i out = 3 a 8.3.3 current limit and short circuit the LMR33630 incorporates valley current limit for normal overloads and for short-circuit protection. in addition the high-side power mosfet is protected from excessive current by a peak current limit circuit. cycle-by-cycle current limit is used for overloads, while hiccup mode is used for short circuits. finally, a zero current detector is used on the low-side power mosfet to implement dem at light loads (see glossary ). the typical value of this current limit is found under i zc in the electrical characteristics . during overloads the low-side current limit, i limit , (see electrical characteristics table) determines the maximum load current that the LMR33630 can supply. when the low-side switch turns on, the inductor current begins to ramp down. if the current does not fall below i limit before the next turnon cycle, then that cycle is skipped, and the low-side mosfet is left on until the current falls below i limit . this is somewhat different than the more typical peak current limit and results in equation 1 for the maximum load current. where ? f sw = switching frequency ? l = inductor value (1) if, during current limit, the voltage on the fb input falls below about 0.4 v, due to a short circuit, the device enters into hiccup mode. in this mode the device stops switching for t hc (see system characteristics ), or about 94 ms and then goes through a normal re-start with soft start. if the short-circuit condition remains, the device runs in current limit for about 20 ms (typical) and then shuts down again. this cycle repeats, as shown in figure 11 as long as the short-circuit-condition persists. this mode of operation helps to reduce the temperature rise of the device during a hard short on the output. the output current is greatly reduced during hiccup mode (see typical characteristics ). once the output short is removed, and the hiccup delay is passed, the output voltage recovers normally as shown in figure 12 the high-side-current limit trips when the peak inductor current reaches i sc (see electrical characteristics table). this is a cycle-by-cycle current limit and does not produce any frequency or load current fold back. it is meant to protect the high-side mosfet from excessive current. under some conditions, such as high input voltages, this current limit may trip before the low-side protection. under this condition, i sc determines the maximum output current. note that i sc varies with duty cycle. en, 3v/div vout, 2v/div pg, 5v/div inductor current, 3a/div 2ms/div in out sw out in limit max out v v l f2 v v i i ? ? ?
14 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated feature description (continued) figure 11. inductor current burst in short-circuit mode figure 12. short-circuit transient and recovery 8.3.4 undervoltage lockout and thermal shutdown the LMR33630 incorporates an undervoltage-lockout feature on the output of the internal ldo (at the vcc pin). when vcc reaches about 3.7 v the device is ready to receive an en signal and start up. when vcc falls below about 3 v the device shuts down, regardless of en status. since the ldo is in dropout during these transitions, the above values roughly represent the input voltage levels during the transitions. thermal shutdown is provided to protect the regulator from excessive junction temperature. when the junction temperature reaches about 165 c the device shuts down; re-start occurs when the temperature falls to about 148 c . 8.4 device functional modes 8.4.1 auto mode in auto mode the device moves between pwm and pfm as the load changes. at light loads the regulator operates in pfm. at higher loads the mode changes to pwm. the load current for which the device moves from pfm to pwm can be found in the application curves . the output current at which the device changes modes depends somewhat on the input voltage; as shown in the curves. for output currents above the curve, the device is in pwm mode. for currents below the curve, the device is in pfm. in pwm the regulator operates as a constant frequency, current mode, full synchronous converter using pwm to regulate the output voltage. while operating in this mode the output voltage is regulated by switching at a constant frequency and modulating the duty cycle to control the power to the load. this provides excellent line and load regulation and low output voltage ripple. in pfm the high-side mosfet is turned on in a burst of one or more pulses to provide energy to the load. the duration of the burst depends on how long it takes the inductor current to reach i peak-min . the frequency of these bursts is adjusted to regulate the output, while diode emulation (dem) is used to maximize efficiency (see glossary ). this mode provides high light-load efficiency by reducing the amount of input supply current required to regulate the output voltage at small loads. this trades off very good light-load efficiency for larger output voltage ripple and variable switching frequency. also, a small increase in output voltage occurs at light loads. the actual switching frequency and output voltage ripple depends on the input voltage, output voltage, and load. typical switching waveforms in pfm and pwm are shown in figure 13 and figure 14 . see the application curves for output voltage variation with load in auto mode. inductor current, 1a/div 50ms/div inductor current, 1a/div vout, 2v/div 50ms/div short applied short removed
15 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated device functional modes (continued) figure 13. typical pfm switching waveforms v in = 12 v, v out = 5 v, i out = 10 ma figure 14. typical pwm switching waveforms v in = 12 v, v out = 5 v, i out = 3 a, ? s = 400 khz 8.4.2 dropout the dropout performance of any buck regulator is affected by the r dson of the power mosfets, the dc resistance of the inductor, and the maximum duty cycle that the controller can achieve. as the input voltage is reduced to near the output voltage, the off-time of the high side mosfet starts to approach the minimum value (see timing characteristics ). beyond this point the switching may become erratic and/or the output voltage will fall out of regulation. to avoid this problem the LMR33630 automatically reduces the switching frequency to increase the effective duty cycle and maintain regulation. in this data sheet the drop-out voltage is defined as the difference between the input and output voltage when the output has dropped by 1% of its nominal value. under this condition the switching frequency has dropped to its minimum value of about 140 khz. see application curves for typical values of dropout voltage under various conditions. note that the 0.4 v short circuit detection threshold is not activated when in dropout mode. typical drop-out characteristics can be found in figure 15 and figure 16 . figure 15. overall dropout characteristic v out = 5 v figure 16. typical drop-out voltage vs output current ? sw = 140 khz 3 3.5 4 4.5 5 5.5 6 4 4.5 5 5.5 6 6.5 7 output voltage (v) input voltage (v) 1a 2a 3a 0a c017 sw, 5v/div vout, 10mv/div inductor current, 0.5a/div 50s/div 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0 0.5 1 1.5 2 2.5 3 3.5 drop-out voltage (v) output current (a) 5v 3.3v c011 2s/div inductor current, 2a/div vout, 10mv/div sw, 5v/div
16 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated device functional modes (continued) 8.4.3 minimum switch on-time every switching regulator has a minimum controllable on-time dictated by the inherent delays and blanking times associated with the control circuits. this imposes a minimum switch duty cycle and therefore a minimum conversion ratio. the constraint is encountered at high input voltages and low output voltages. to help extend the minimum controllable duty cycle, the LMR33630 automatically reduces the switching frequency when the minimum on-time limit is reached. in this way the converter can regulate the lowest programmable output voltage at the maximum input voltage. an estimate for the approximate input voltage, for a given output voltage, before frequency fold-back occurs is found in equation 2 . the values of t on and f sw can be found in the electrical characteristics table. as the input voltage is increased, the switch on-time (duty-cycle) reduces to regulate the output voltage. when the on-time reaches the limit, the switching frequency drops, while the on-time remains fixed. this relationship is highlighted in figure 17 for a nominal switching frequency of 2.1 mhz. (2) figure 17. switching frequency vs input voltage v out = 3.3 v, i out = 1 a 1 1.2 1.4 1.6 1.8 2 2.2 2.4 10 15 20 25 30 35 40 switching frequency (mhz) input voltage (v) 3.3v c017 sw on out in f t v v ? d
17 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 9 application and implementation note information in the following applications sections is not part of the ti component specification, and ti does not warrant its accuracy or completeness. ti ? s customers are responsible for determining suitability of components for their purposes. customers should validate and test their design implementation to confirm system functionality. note all of the capacitance values given in the following application information refer to effective values; unless otherwise stated. the effective value is defined as the actual capacitance under d.c. bias and temperature; not the rated or nameplate values. use high-quality, low-esr, ceramic capacitors with an x5r or better dielectric throughout. all high value ceramic capacitors have a large voltage coefficient in addition to normal tolerances and temperature effects. under d.c. bias the capacitance drops considerably. large case sizes and/or higher voltage ratings are better in this regard. to help mitigate these effects, multiple capacitors can be used in parallel to bring the minimum effective capacitance up to the required value. this can also ease the rms current requirements on a single capacitor. a careful study of bias and temperature variation of any capacitor bank should be made in order to ensure that the minimum value of effective capacitance is provided. 9.1 application information the LMR33630 step-down dc-to-dc converter is typically used to convert a higher dc voltage to a lower dc voltage with a maximum output current of 3 a. the following design procedure can be used to select components for the LMR33630. alternately, the webench ? design tool may be used to generate a complete design. this tool utilizes an iterative design procedure and has access to a comprehensive database of components. this allows the tool to create an optimized design and allows the user to experiment with various options. 9.2 typical application figure 18 shows a typical application circuit for the LMR33630. this device is designed to function over a wide range of external components and system parameters. however, the internal compensation is optimized for a certain range of external inductance and output capacitance. as a quick start guide, table 2 provides typical component values for a range of the most common output voltages. the values given in the table are typical. other values may be used to enhance certain performance criterion as required by the application. figure 18. example application circuit (400 khz) vin en vcc agnd pgnd sw boot fb v in v out l c boot c out c in c vcc 10 f 4x 22 f 8 h 0.1 f 1 f c ff r fbt r fbb 100 n? 24.9 n? 6 v to 36 v 5 v pg pg c hf 10 n? 220 nf 3 a
18 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated typical application (continued) 9.2.1 design requirements table 1 provides a detailed design procedure: table 1. detailed design parameters design parameter example value input voltage 12 v (6 v to 36 v) output voltage 5 v maximum output current 0 a to 3 a switching frequency 400 khz table 2. typical external component values ? sw (khz) v out (v) l ( h) c out (rated capacitance) r fbt ( ) r fbb ( ) c in c boot c vcc c ff 400 3.3 6.8 4 22 f 100 k 43.2 k 10 f + 220 nf 100 nf 1 f open 1400 3.3 2.2 2 22 f 100 k 43.2 k 10 f + 220 nf 100 nf 1 f open 2100 3.3 1.2 2 22 f 100 k 43.2 k 10 f + 220 nf 100 nf 1 f open 400 5 8 4 22 f 100 k 24.9 k 10 f + 220 nf 100 nf 1 f open 1400 5 2.2 2 22 f 100 k 24.9 k 10 f + 220 nf 100 nf 1 f open 2100 5 1.5 2 22 f 100 k 24.9 k 10 f + 220 nf 100 nf 1 f open 400 12 15 4 22 f 100 k 9.09 k 10 f + 220 nf 100 nf 1 f open 1400 12 4.7 4 10 f 100 k 9.09 k 10 f + 220 nf 100 nf 1 f open 2100 12 3.3 4 10 f 100 k 9.09 k 10 f + 220 nf 100 nf 1 f open 9.2.2 detailed design procedure the following design procedure applies to figure 18 and table 1 . 9.2.2.1 custom design with webench ? tools click here to create a custom design using the LMR33630 device with the webench ? power designer. 1. start by entering the input voltage (v in ), output voltage (v out ), and output current (i out ) requirements. 2. optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial. 3. compare the generated design with other possible solutions from texas instruments. the webench power designer provides a customized schematic along with a list of materials with real-time pricing and component availability. in most cases, these actions are available: ? run electrical simulations to see important waveforms and circuit performance ? run thermal simulations to understand board thermal performance ? export customized schematic and layout into popular cad formats ? print pdf reports for the design, and share the design with colleagues get more information about webench tools at www.ti.com/webench . 9.2.2.2 choosing the switching frequency the choice of switching frequency is a compromise between conversion efficiency and overall solution size. lower switching frequency implies reduced switching losses and usually results in higher system efficiency. however, higher switching frequency allows the use of smaller inductors and output capacitors, and hence a more compact design. for this example we choose 400 khz.
19 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 9.2.2.3 setting the output voltage the output voltage of LMR33630 is externally adjustable using a resistor divider network. the range of recommended output voltage is found in the recommended operating conditions table. the divider network is comprised of r fbt and r fbb , and closes the loop between the output voltage and the converter. the converter regulates the output voltage by holding the voltage on the fb pin equal to the internal reference voltage, v ref . the resistance of the divider is a compromise between excessive noise pick-up and excessive loading of the output. smaller values of resistance reduce noise sensitivity but also reduce the light-load efficiency. the recommended value for r fbt is 100 k ; with a maximum value of 1 m . if a 1 m is selected for r fbt , then a feed-forward capacitor must be used across this resistor to provide adequate loop phase margin (see c ff selection ). once r fbt is selected, equation 3 is used to select r fbb . v ref is nominally 1 v (see electrical characteristics for limits). (3) for this 5-v example, r fbt = 100 k and r fbb = 24.9 k was chosen. 9.2.2.4 inductor selection the parameters for selecting the inductor are the inductance and saturation current. the inductance is based on the desired peak-to-peak ripple current and is normally chosen to be in the range of 20% to 40% of the maximum output current. experience shows that the best value for inductor ripple current is 30% of the maximum load current. note that when selecting the ripple current for applications with much smaller maximum load than the maximum available from the device, the maximum device current should be used. equation 4 can be used to determine the value of inductance. the constant k is the percentage of inductor current ripple. for this example we choose k = 0.3 and find an inductance l = 8.1 h; we select the next standard value of 8 h. (4) ideally, the saturation current rating of the inductor should be at least as large as the high-side switch current limit, i sc (see electrical characteristics ). this ensures that the inductor does not saturate even during a short circuit on the output. when the inductor core material saturates, the inductance falls to a very low value, causing the inductor current to rise very rapidly. although the valley current limit, i limit , is designed to reduce the risk of current run-away, a saturated inductor can cause the current to rise to high values very rapidly. this may lead to component damage; do not allow the inductor to saturate! inductors with a ferrite core material have very hard saturation characteristics, but usually have lower core losses than powdered iron cores. powered iron cores exhibit a soft saturation, allowing some relaxation in the current rating of the inductor. however, they have more core losses at frequencies above about 1 mhz. in any case the inductor saturation current should not be less than the device low-side current limit, i limit (see electrical characteristics ). in order to avoid sub-harmonic oscillation, the inductance value should not be less than that given in equation 5 the maximum inductance is limited by the minimum current ripple required for the current mode control to perform correctly. as a rule-of- thumb, the minimum inductor ripple current should be no less than about 10% of the device maximum rated current under nominal conditions. (5) 9.2.2.5 output capacitor selection the value of the output capacitor, and its esr, determine the output voltage ripple and load transient performance. the output capacitor bank is usually limited by the load transient requirements, rather than the output voltage ripple. equation 6 can be used to estimate a lower bound on the total output capacitance, and an upper bound on the esr, required to meet a specified load transient. sw out min f v 28.0 l ? t in out max out sw out in v v ik f v v l ? ?? ? ? o ? ? a 1 v v r r ref out fbt fbb
20 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated where ? v out = output voltage transient ? i out = output current transient ? k = ripple factor from inductor selection (6) once the output capacitor and esr have been calculated, equation 7 can be used to check the peak-to-peak output voltage ripple; v r . (7) the output capacitor and esr can then be adjusted to meet both the load transient and output ripple requirements. for this example we require a v out of 250 mv for an output current step of i out = 2 a. equation 6 gives a minimum value of 52 f and a maximum esr of 0.11 . assuming a 20% tolerance and a 10% bias de-rating, we arrive at a minimum capacitance of 72 f. this can be achieved with a bank of 4 22- f, 16-v, ceramic capacitors in the 1210 case size. more output capacitance can be used to improve the load transient response. ceramic capacitors can easily meet the minimum esr requirements. in some cases an aluminum electrolytic capacitor can be placed in parallel with the ceramics to help build up the required value of capacitance. in general use a capacitor of at least 10 v for output voltages of 3.3 v or less, while a capacitor of 16 v or more should be used for output voltages of 5 v and above. in practice the output capacitor has the most influence on the transient response and loop phase margin. load transient testing and bode plots are the best way to validate any given design and should always be completed before the application goes into production. in addition to the required output capacitance, a small ceramic placed on the output can help to reduce high frequency noise. small case size ceramic capacitors in the range of 1 nf to 100 nf can be very helpful in reducing spikes on the output caused by inductor and board parasitics. the maximum value of total output capacitance should be limited to about 10 times the design value, or 1000 f, whichever is smaller. large values of output capacitance can adversely affect the start-up behavior of the regulator as well as the loop stability. if values larger than noted here must be used, then a careful study of start- up at full load and loop stability must be performed. 9.2.2.6 input capacitor selection the ceramic input capacitors provide a low impedance source to the regulator in addition to supplying the ripple current and isolating switching noise from other circuits. a minimum of 10 f of ceramic capacitance is required on the input of the LMR33630. this must be rated for at least the maximum input voltage that the application requires; preferably twice the maximum input voltage. this capacitance can be increased to help reduce input voltage ripple and/or maintain the input voltage during load transients. in addition a small case size 220-nf ceramic capacitor must be used at the input, as close a possible to the regulator. this provides a high frequency bypass for the control circuits internal to the device. for this example a 10- f, 50-v, x7r (or better) ceramic capacitor is chosen. the 220 nf must also be rated at 50 v with an x7r dielectric. in out 2 out out 2 out sw out out v v d )d 1( 1 1 12 k k 1 i 2 v k 2 esr d 2 12 k k 1 d 1 k v f i c ? ? ? o ? ? ? a ? ? 1 ? ? '? '? d ? ? ? o ? ? ? a ? ? ? ? '? ' t 2 out sw 2 l r c f8 1 esr i v ? ? ? '#
21 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated many times it is desirable to use an electrolytic capacitor on the input in parallel with the ceramics. this is especially true if long leads/traces are used to connect the input supply to the regulator. the moderate esr of this capacitor can help damp any ringing on the input supply caused by the long power leads. the use of this additional capacitor also helps with voltage dips caused by input supplies with unusually high impedance. most of the input switching current passes through the ceramic input capacitor(s). the approximate rms value of this current can be calculated from equation 8 and should be checked against the manufacturers' maximum ratings. (8) 9.2.2.7 c boot the LMR33630 requires a boot-strap capacitor connected between the boot pin and the sw pin. this capacitor stores energy that is used to supply the gate drivers for the power mosfets. a high-quality ceramic capacitor of 100 nf and at least 16 v is required. 9.2.2.8 vcc the vcc pin is the output of the internal ldo used to supply the control circuits of the regulator. this output requires a 1- f, 16-v ceramic capacitor connected from vcc to gnd for proper operation. in general this output should not be loaded with any external circuitry. however, this output can be used to supply the pull-up for the power-good function (see power-good flag output ). a value of 100 k is a good choice in this case. the nominal output voltage on vcc is 5 v; see electrical characteristics for limits. 9.2.2.9 c ff selection in some cases a feed-forward capacitor can be used across r fbt to improve the load transient response or improve the loop-phase margin. this is especially true when values of r fbt > 100 k are used. large values of r fbt , in combination with the parasitic capacitance at the fb pin, can create a small signal pole that interferes with the loop stability. a c ff can help to mitigate this effect. equation 9 can be used to estimate the value of c ff . the value found with equation 9 is a starting point; use lower values to determine if any advantage is gained by the use of a c ff capacitor. the application report optimizing transient response of internally compensated dc- dc converters with feed-forward capacitor is helpful when experimenting with a feed-forward capacitor. (9) 9.2.2.9.1 external uvlo in some cases an input uvlo level different than that provided internal to the device is needed. this can be accomplished by using the circuit shown in figure 19 can be used. the input voltage at which the device turns on is designated v on ; while the turnoff voltage is v off . first a value for r enb is chosen in the range of 10 k to 100 k and then equation 10 is used to calculate r ent and v off . figure 19. set-up for external uvlo application 2 i i out rms # out ref fbt out out ff v v r 120 c v c ? ? ? en r ent r enb vin
22 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated where ? v on = v in turnon voltage ? v off = v in turnoff voltage (10) 9.2.2.10 maximum ambient temperature as with any power conversion device, the LMR33630 dissipates internal power while operating. the effect of this power dissipation is to raise the internal temperature of the converter above ambient. the internal die temperature (t j ) is a function of the ambient temperature, the power loss and the effective thermal resistance, r ja of the device and pcb combination. the maximum internal die temperature for the LMR33630 must be limited to 125 c. this establishes a limit on the maximum device power dissipation and therefore the load current. equation 11 shows the relationships between the important parameters. it is easy to see that larger ambient temperatures (t a ) and larger values of r ja reduce the maximum available output current. the converter efficiency can be estimated by using the curves provided in this data sheet. if the desired operating conditions can not be found in one of the curves, then interpolation can be used to estimate the efficiency. alternatively, the evm can be adjusted to match the desired application requirements and the efficiency can be measured directly. the correct value of r ja is more difficult to estimate. as stated in semiconductor and ic package thermal metrics , the values given in the thermal information table are not valid for design purposes and must not be used to estimate the thermal performance of the application. the values reported in that table were measured under a specific set of conditions that are rarely obtained in an actual application. where ? = efficiency (11) the effective r ja is a critical parameter and depends on many factors such as power dissipation, air temperature/flow, pcb area, copper heat-sink area, number of thermal vias under the package, and adjacent component placement; to mention just a few. the hsoic (dda) package utilizes a die attach paddle, or thermal pad (pad) to provide a place to solder down to the pcb heat-sinking copper. this provides a good heat conduction path from the regulator junction to the heat sink and must be properly soldered to the pcb heat sink copper. a typical example of r ja vs copper board area can be found in figure 20 . the copper area given in the graph is for each layer; the top and bottom layers are 2 oz. copper each, while the inner layers are 1 oz. a typical curve of maximum output current vs. ambient temperature is shown in figure 21 . this data was taken with a device/pcb combination giving an r ja of about 30 c/w. it must be remembered that the data given in these graphs are for illustration purposes only, and the actual performance in any given application depends on all of the previously mentioned factors. out ja a j max out v 1 1 r t t i ? k k ? t ? ? 1 ? ? ? ? ? 1 ? en hys en on off enb h en on ent v v 1 v v r 1 v v r
23 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated figure 20. typical r ja vs copper area for a four-layer board and the hsoic (dda) package figure 21. maximum output current vs ambient temperature v in = 12 v, v out = 5 v, ? sw = 400 khz, r ja = 30 c/w the resources below can be used as a guide to optimal thermal pcb design and estimating r ja for a given application environment: ? thermal design by insight not hindsight ? a guide to board layout for best thermal resistance for exposed pad packages ? semiconductor and ic package thermal metrics ? thermal design made simple with lm43603 and lm43602 ? slma002 powerpad tm thermally enhanced package ? powerpad tm made easy ? sbva025 using new thermal metrics 0 0.5 1 1.5 2 2.5 3 3.5 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 maximum output current (a) ambient temperature ( ? c) c002 20 22 24 26 28 30 32 34 36 38 40 42 44 0 10 20 30 40 50 60 70 r ja ( ? c/w) copper area (cm 2 ) dda, 4l c003
24 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 9.2.3 application curves unless otherwise specified the following conditions apply: v in = 12 v, t a = 25 c. the circuit is shown in figure 40 , with the appropriate bom from table 3 . v out = 5 v 400 khz dda package figure 22. efficiency v out = 3.3 v 400 khz dda package figure 23. efficiency v out = 5 v 1.4 mhz dda package figure 24. efficiency v out = 3.3 v 1.4 mhz dda package figure 25. efficiency v out = 5 v 2.1 mhz dda package figure 26. efficiency v out = 3.3 v 2.1 mhz dda package figure 27. efficiency 55 60 65 70 75 80 85 90 95 100 0.001 0.01 0.1 1 10 efficiency (%) output current (a) 8v 12v 24v 36v c009 40 45 50 55 60 65 70 75 80 85 90 95 100 0.001 0.01 0.1 1 10 efficiency (%) output current (a) 8v 12v 24v 36v c014 40 45 50 55 60 65 70 75 80 85 90 95 100 0.001 0.01 0.1 1 10 efficiency (%) output current (a) 5v 12v 24v 36v c015 40 45 50 55 60 65 70 75 80 85 90 95 100 0.001 0.01 0.1 1 10 efficiency (%) output current (a) 5v 12v 24v 36v c012 40 45 50 55 60 65 70 75 80 85 90 95 100 0.001 0.01 0.1 1 10 efficiency (%) output current (a) 8v 12v 24v 36v c013 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.001 0.01 0.1 1 10 efficiency (%) output current (a) 5v 12v 24v 36v c011
25 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated unless otherwise specified the following conditions apply: v in = 12 v, t a = 25 c. the circuit is shown in figure 40 , with the appropriate bom from table 3 . v out = 5 v figure 28. line and load regulation v out = 5 v i out = 0 a r fbt = 1 m figure 29. input supply current v out = 5 v figure 30. mode change thresholds v out = 5 v ? sw = 400 khz figure 31. switching frequency vs output current v in = 12 v v out = 5 v t f = t r = 2 s i out = 0 a to 3 a figure 32. load transient v in = 12 v v out = 5 v t f = t r = 2 s i out = 1 a to 3 a figure 33. load transient 1 10 100 1000 10000 100000 1000000 10000000 0.00001 0.0001 0.001 0.01 0.1 1 10 switching frequency (hz) output current (a) 8v 12v 24v 36v c014 5.01 5.015 5.02 5.025 5.03 5.035 5.04 5.045 5.05 5.055 5.06 0 0.5 1 1.5 2 2.5 3 3.5 output voltage (v) output current (a) 8v 12v 24v 36v c011 20 22 24 26 28 30 32 0 5 10 15 20 25 30 35 40 input supply current (a) input voltage (v) 5v c017 output current, 1a/div 100 s/div vout, 300mv/div 0 0 100 s/div vout, 300mv/div output current, 1a/div 0 0.1 0.2 0.3 0.4 0.5 0.6 0 5 10 15 20 25 30 35 40 output current (a) input voltage (v) 5v c012 pwm pfm 9 ;
26 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated unless otherwise specified the following conditions apply: v in = 12 v, t a = 25 c. the circuit is shown in figure 40 , with the appropriate bom from table 3 . v out = 3.3 v figure 34. line and load regulation v out = 3.3 v i out = 0 a r fbt = 1 m figure 35. input supply current v out = 3.3v figure 36. mode change thresholds v out = 3.3 v ? sw = 400 khz figure 37. switching frequency vs output current v in = 12 v v out = 3.3 v t f = t r = 2 s i out = 0 a to 3 a figure 38. load transient v in = 12 v v out = 3.3v i out = 1 a to 3 a t f = t r = 2 s figure 39. load transient output current, 1a/div vout, 300mv/div 100 s/div 0 3.31 3.315 3.32 3.325 3.33 3.335 3.34 3.345 3.35 0 0.5 1 1.5 2 2.5 3 3.5 output voltage (v) output current (a) 5v 12v 24v 36v c011 20 22 24 26 28 30 32 0 5 10 15 20 25 30 35 40 input supply current (a) input voltage (v) 3.3v c016 1 10 100 1000 10000 100000 1000000 10000000 0.00001 0.0001 0.001 0.01 0.1 1 10 switching frequency (hz) output current (a) 5v 12v 24v 36v c015 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 5 10 15 20 25 30 35 40 output current (a) input voltage (v) 3.3v c012 pwm pfm 9 ; vout, 300mv/div output current, 1a/div 100 s/div 0
27 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated unless otherwise specified the following conditions apply: v in = 12 v, t a = 25 c. the circuit is shown in figure 40 , with the appropriate bom from table 3 . (1) the values in this table were selected to enhance certain performance criteria and may not represent typical values. figure 40. circuit for typical application curves table 3. bom for typical application curves dda package (1) v out frequency r fbb c out l u1 3.3 v 400 khz 43.3 k 4 22 f 6.8 h, 14 m LMR33630adda 3.3 v 1400 khz 43.3 k 4 22 f 2.2 h, 11.4 m LMR33630bdda 3.3 v 2100 khz 43.3 k 4 22 f 1.2 h, 16 m LMR33630cdda 5 v 400 khz 24.9 k 4 22 f 8 h, 14 m LMR33630adda 5 v 1400 khz 24.9 k 4 22 f 2.2 h, 11.4 m LMR33630bdda 5 v 2100 khz 24.9 k 4 22 f 1.5 h, 8.2 m LMR33630cdda 9.3 do ' s and don ' ts ? don't: exceed the absolute maximum ratings ? don't: exceed the esd ratings ? don't: exceed the recommended operating conditions ? don't: allow the en input to float. ? don't: allow the output voltage to exceed the input voltage, nor go below ground. ? don't: use the thermal data given in the thermal information table to design your application. ? do: follow all the guidelines and/or suggestions found in this data sheet before committing the design to production. ti application engineers are ready to help critique your design and pcb layout to help make your project a success (see community resources ). vin en vcc agnd pgnd sw boot fb v in v out l c boot c out c in c vcc 10 f 0.1 f 1 f r fbt r fbb pg pg c hf 10 n? 220 nf u1 100 n?
28 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 10 power supply recommendations the characteristics of the input supply must be compatible with the absolute maximum ratings and recommended operating conditions found in this data sheet. in addition, the input supply must be capable of delivering the required input current to the loaded regulator. the average input current can be estimated with equation 12 , where is the efficiency. (12) if the regulator is connected to the input supply through long wires or pcb traces, special care is required to achieve good performance. the parasitic inductance and resistance of the input cables can have an adverse effect on the operation of the regulator. the parasitic inductance, in combination with the low-esr, ceramic input capacitors, can form an under damped resonant circuit, resulting in overvoltage transients at the input to the regulator. the parasitic resistance can cause the voltage at the vin pin to dip whenever a load transient is applied to the output. if the application is operating close to the minimum input voltage, this dip may cause the regulator to momentarily shutdown and/or reset. the best way to solve these kind of issues is to reduce the distance from the input supply to the regulator and/or use an aluminum or tantalum input capacitor in parallel with the ceramics. the moderate esr of these types of capacitors help to damp the input resonant circuit and reduce any overshoots. a value in the range of 20 f to 100 f is usually sufficient to provide input damping and help to hold the input voltage steady during large load transients. sometimes, for other system considerations, an input filter is used in front of the regulator. this can lead to instability, as well as some of the effects mentioned above, unless it is designed carefully. the user guide an- 2162 simple success with conducted emi from dcdc converters provides helpful suggestions when designing an input filter for any switching regulator. in some cases a transient voltage suppressor (tvs) is used on the input of regulators. one class of this device has a snap-back characteristic (thyristor type). the use of a device with this type of characteristic is not recommended. when the tvs fires, the clamping voltage falls to a very low value. if this voltage is less than the output voltage of the regulator, the output capacitors discharge through the device back to the input. this uncontrolled current flow may damage the device. k? ? in out out in v i v i
29 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 11 layout 11.1 layout guidelines the pcb layout of any dc/dc converter is critical to the optimal performance of the design. bad pcb layout can disrupt the operation of an otherwise good schematic design. even if the converter regulates correctly, bad pcb layout can mean the difference between a robust design and one that cannot be mass produced. furthermore, the emi performance of the regulator is dependent on the pcb layout, to a great extent. in a buck converter the most critical pcb feature is the loop formed by the input capacitor(s) and power ground, as shown in figure 41 . this loop carries large transient currents that can cause large transient voltages when reacting with the trace inductance. these unwanted transient voltages will disrupt the proper operation of the converter. because of this, the traces in this loop should be wide and short, and the loop area as small as possible to reduce the parasitic inductance. figure 42 shows a recommended layout for the critical components of the LMR33630dda . 1. place the input capacitor(s) as close as possible to the vin and gnd terminals. vin and gnd pins are adjacent, simplifying the input capacitor placement. 2. place bypass capacitor for vcc close to the vcc pin. this capacitor must be placed close to the device and routed with short, wide traces to the vcc and gnd pins. 3. use wide traces for the c boot capacitor. place c boot close to the device with short/wide traces to the boot and sw pins. 4. place the feedback divider as close as possible to the fb pin of the device. place r fbb , r fbt , and c ff , if used, physically close to the device. the connections to fb and gnd must be short and close to those pins on the device. the connection to v out can be somewhat longer. however, this latter trace must not be routed near any noise source (such as the sw node) that can capacitively couple into the feedback path of the regulator. 5. use at least one ground plane in one of the middle layers. this plane acts as a noise shield and also act as a heat dissipation path. 6. connect the thermal pad to the ground plane. the soic package has a thermal pad (pad) connection that must be soldered down to the pcb ground plane. this pad acts as a heat-sink connection and an electrical ground connection for the regulator. the integrity of this solder connection has a direct bearing on the total effective r ja of the application. 7. provide wide paths for vin, vout, and gnd. making these paths as wide and direct as possible reduces any voltage drops on the input or output paths of the converter and maximizes efficiency. 8. provide enough pcb area for proper heat-sinking. as stated in the maximum ambient temperature section, enough copper area must be used to ensure a low r ja , commensurate with the maximum load current and ambient temperature. make the top and bottom pcb layerswith two-ounce copper; and no less than one ounce. with the soic package, use an array of heat-sinking vias to connect the thermal pad (pad) to the ground plane on the bottom pcb layer. if the pcb design uses multiple copper layers (recommended), these thermal vias can also be connected to the inner layer heat-spreading ground planes. 9. keep switch area small. keep the copper area connecting the sw pin to the inductor as short and wide as possible. at the same time the total area of this node should be minimized to help reduce radiated emi. see the following pcb layout resources for additional important guidelines: ? layout guidelines for switching power supplies ? simple switcher pcb layout guidelines ? construction your power supply- layout considerations ? low radiated emi layout made simple with lm4360x and lm4600x
30 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated layout guidelines (continued) figure 41. current loops with fast edges 11.1.1 ground and thermal considerations as mentioned above, ti recommends using one of the middle layers as a solid ground plane. a ground plane provides shielding for sensitive circuits and traces. it also provides a quiet reference potential for the control circuitry. the agnd and pgnd pins should be connected to the ground planes using vias next to the bypass capacitors. pgnd pins are connected directly to the source of the low side mosfet switch, and also connected directly to the grounds of the input and output capacitors. the pgnd net contains noise at the switching frequency and may bounce due to load variations. the pgnd trace, as well as the vin and sw traces, must be constrained to one side of the ground planes. the other side of the ground plane contains much less noise and must be used for sensitive routes. ti recommends providing adequate device heat sinking by utilizing the thermal pad (pad) of the device as the primary thermal path. use a minimum 4 3 array of 10 mil thermal vias to connect the pad to the system ground plane heat sink. the vias must be evenly distributed under the pad. use as much copper as possible, for system ground plane, on the top and bottom layers for the best heat dissipation. use a four-layer board with the copper thickness for the four layers, starting from the top as: 2 oz / 1 oz / 1 oz / 2 oz. a four-layer board with enough copper thickness, and proper layout, provides low current conduction impedance, proper shielding and lower thermal resistance. c in vin sw gnd
31 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 11.2 layout example figure 42. example layout for hsoic (dda) package vin gnd vout gnd gnd heatsink gnd heatsink c out c out c out c in r fbb r fbt c hf c vcc c boot en pgood inductor bottom trace via ground plane top trace via bottom
32 LMR33630 snvsan3a ? august 2017 ? revised february 2018 www.ti.com product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 12 device and documentation support 12.1 device support 12.1.1 development support 12.1.1.1 custom design with webench ? tools click here to create a custom design using the lm33630 device with the webench ? power designer. 1. start by entering the input voltage (v in ), output voltage (v out ), and output current (i out ) requirements. 2. optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial. 3. compare the generated design with other possible solutions from texas instruments. the webench power designer provides a customized schematic along with a list of materials with real-time pricing and component availability. in most cases, these actions are available: ? run electrical simulations to see important waveforms and circuit performance ? run thermal simulations to understand board thermal performance ? export customized schematic and layout into popular cad formats ? print pdf reports for the design, and share the design with colleagues get more information about webench tools at www.ti.com/webench . 12.2 documentation support 12.2.1 related documentation for related documentation see the following: ? thermal design by insight not hindsight ? a guide to board layout for best thermal resistance for exposed pad packages ? semiconductor and ic package thermal metrics ? thermal design made simple with lm43603 and lm43602 ? slma002 powerpad tm thermally enhanced package ? powerpad tm made easy ? sbva025 using new thermal metrics ? layout guidelines for switching power supplies ? simple switcher pcb layout guidelines ? construction your power supply- layout considerations ? low radiated emi layout made simple with lm4360x and lm4600x 12.3 receiving notification of documentation updates to receive notification of documentation updates, navigate to the device product folder on ti.com. in the upper right corner, click on alert me to register and receive a weekly digest of any product information that has changed. for change details, review the revision history included in any revised document. 12.4 community resources the following links connect to ti community resources. linked contents are provided "as is" by the respective contributors. they do not constitute ti specifications and do not necessarily reflect ti's views; see ti's terms of use . ti e2e ? online community ti's engineer-to-engineer (e2e) community. created to foster collaboration among engineers. at e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. design support ti's design support quickly find helpful e2e forums along with design support tools and contact information for technical support.
33 LMR33630 www.ti.com snvsan3a ? august 2017 ? revised february 2018 product folder links: LMR33630 submit documentation feedback copyright ? 2017 ? 2018, texas instruments incorporated 12.5 trademarks powerpad, e2e are trademarks of texas instruments. simple switcher, webench are registered trademarks of texas instruments. all other trademarks are the property of their respective owners. 12.6 electrostatic discharge caution these devices have limited built-in esd protection. the leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the mos gates. 12.7 glossary slyz022 ? ti glossary . this glossary lists and explains terms, acronyms, and definitions. 13 mechanical, packaging, and orderable information the following pages include mechanical, packaging, and orderable information. this information is the most current data available for the designated devices. this data is subject to change without notice and revision of this document. for browser-based versions of this data sheet, refer to the left-hand navigation.
package option addendum www.ti.com 9-mar-2018 addendum-page 1 packaging information orderable device status (1) package type package drawing pins package qty eco plan (2) lead/ball finish (6) msl peak temp (3) op temp (c) device marking (4/5) samples LMR33630adda active so powerpad dda 8 75 green (rohs & no sb/br) cu nipdauag level-2-260c-1 year -40 to 125 33630a LMR33630addar active so powerpad dda 8 2500 green (rohs & no sb/br) cu nipdauag level-2-260c-1 year -40 to 125 33630a LMR33630bdda active so powerpad dda 8 75 green (rohs & no sb/br) cu nipdauag level-2-260c-1 year -40 to 125 33630b LMR33630bddar active so powerpad dda 8 2500 green (rohs & no sb/br) cu nipdauag level-2-260c-1 year -40 to 125 33630b LMR33630cdda active so powerpad dda 8 75 green (rohs & no sb/br) cu nipdauag level-2-260c-1 year -40 to 125 33630c LMR33630cddar active so powerpad dda 8 2500 green (rohs & no sb/br) cu nipdauag level-2-260c-1 year -40 to 125 33630c (1) the marketing status values are defined as follows: active: product device recommended for new designs. lifebuy: ti has announced that the device will be discontinued, and a lifetime-buy period is in effect. nrnd: not recommended for new designs. device is in production to support existing customers, but ti does not recommend using this part in a new design. preview: device has been announced but is not in production. samples may or may not be available. obsolete: ti has discontinued the production of the device. (2) rohs: ti defines "rohs" to mean semiconductor products that are compliant with the current eu rohs requirements for all 10 rohs substances, including the requirement that rohs substance do not exceed 0.1% by weight in homogeneous materials. where designed to be soldered at high temperatures, "rohs" products are suitable for use in specified lead-free processes. ti may reference these types of products as "pb-free". rohs exempt: ti defines "rohs exempt" to mean products that contain lead but are compliant with eu rohs pursuant to a specific eu rohs exemption. green: ti defines "green" to mean the content of chlorine (cl) and bromine (br) based flame retardants meet js709b low halogen requirements of <=1000ppm threshold. antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (3) msl, peak temp. - the moisture sensitivity level rating according to the jedec industry standard classifications, and peak solder temperature. (4) there may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) multiple device markings will be inside parentheses. only one device marking contained in parentheses and separated by a "~" will appear on a device. if a line is indented then it is a continuation of the previous line and the two combined represent the entire device marking for that device.
package option addendum www.ti.com 9-mar-2018 addendum-page 2 (6) lead/ball finish - orderable devices may have multiple material finish options. finish options are separated by a vertical ruled line. lead/ball finish values may wrap to two lines if the finish value exceeds the maximum column width. important information and disclaimer: the information provided on this page represents ti's knowledge and belief as of the date that it is provided. ti bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. efforts are underway to better integrate information from third parties. ti has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. ti and ti suppliers consider certain information to be proprietary, and thus cas numbers and other limited information may not be available for release. in no event shall ti's liability arising out of such information exceed the total purchase price of the ti part(s) at issue in this document sold by ti to customer on an annual basis.
tape and reel information *all dimensions are nominal device package type package drawing pins spq reel diameter (mm) reel width w1 (mm) a0 (mm) b0 (mm) k0 (mm) p1 (mm) w (mm) pin1 quadrant LMR33630addar so power pad dda 8 2500 330.0 12.8 6.4 5.2 2.1 8.0 12.0 q1 LMR33630bddar so power pad dda 8 2500 330.0 12.8 6.4 5.2 2.1 8.0 12.0 q1 LMR33630cddar so power pad dda 8 2500 330.0 12.8 6.4 5.2 2.1 8.0 12.0 q1 package materials information www.ti.com 27-feb-2018 pack materials-page 1
*all dimensions are nominal device package type package drawing pins spq length (mm) width (mm) height (mm) LMR33630addar so powerpad dda 8 2500 366.0 364.0 50.0 LMR33630bddar so powerpad dda 8 2500 366.0 364.0 50.0 LMR33630cddar so powerpad dda 8 2500 366.0 364.0 50.0 package materials information www.ti.com 27-feb-2018 pack materials-page 2

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