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ltc 3374 1 3374f for more information www.linear.com/ltc3374 typical application features description 8-channel parallelable 1a buck dc/dcs the lt c ? 3374 is a high efficiency multioutput power sup- ply ic. the dc/dcs consist of eight synchronous buck converters (1a each) all powered from independent 2.25v to 5.5v input supplies. the dc/dcs may be used independently or in parallel to achieve higher currents of up to 4 a per output with a shared inductor. the common buck switching frequency may be programmed with an external resistor, synchronized to an external oscillator, or set to a default internal 2mhz clock. the operating mode for all dc/dcs may be programmed via the mode pin. to reduce input noise the buck converters are phased in 90 steps. precision enable pin thresholds provide reli- able power-up sequencing. the ltc3374 is available in a compact 38-lead 5mm 7mm qfn package as well as a 38-lead tssop package. 8-channel 1a multioutput buck regulator buck efficiency vs i load applications n 8-channel independent step-down dc/dcs n master-slave configurable for up to 4a per output rail with a single inductor n independent v in supplies for each dc/dc (2.25 v to 5.5v) n all dc/dcs have 0.8v C v in output range n precision enable pin thresholds for autonomous sequencing n 1 mhz to 3mhz programmable/synchronizable oscillator frequency (2mhz default) n die temperature monitor output n thermally enhanced 38-lead qfn (5mm 7mm) and tssop packages n general purpose multichannel power supplies n industrial/automotive/communications l, lt , lt c , lt m , linear technology , the linear logo and burst mode are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. 0.8v to v in1 up to 1a buck1 2.7v to 5.5v v in1 buck2 v in2 buck7 v in7 buck8 v in8 v cc 0.8v to v in2 up to 1a slave master slave master slave master en1 en2 en3 en4 en5 en6 en7 en8 pgood_all temp mode sync 0.8v to v in7 up to 1a 0.8v to v in8 up to 1a rt ltc3374 3374 ta01a ? ? ? load current (ma) 0 0 efficiency (%) 10 30 40 50 100 70 1000 2000 3374 ta01b 20 80 90 60 3000 4000 forced continuous mode v in = 3.3v, v out = 1.8v f osc = 1mhz, l = 3.3h single buck dual buck triple buck quad buck
ltc 3374 2 3374f for more information www.linear.com/ltc3374 table of contents features ..................................................... 1 applications ................................................ 1 typical application ........................................ 1 description .................................................. 1 absolute maximum ratings .............................. 3 pin configuration .......................................... 3 order information .......................................... 3 electrical characteristics ................................. 4 typical performance characteristics ................... 6 pin functions .............................................. 11 block diagram ............................................. 13 operation ................................................... 14 buck switching regulators ..................................... 14 buck regulators with combined power stages ...... 14 power failure reporting via pgood_all pin ........ 15 temperature monitoring and overtemperature protection ............................................................... 15 programming the operating frequency .................. 15 applications information ................................ 17 buck switching regulator output voltage and feedback network ............................................ 17 buck regulators ..................................................... 17 combined buck regulators ..................................... 17 input and output decoupling capacitor selection ... 17 pcb considerations ................................................ 17 package description ..................................... 22 typical application ....................................... 24 related parts .............................................. 24
ltc 3374 3 3374f for more information www.linear.com/ltc3374 pin configuration absolute maximum ratings v in 1-8 , fb 1-8, en 1-8, v cc , pgood_ all , sync , rt , mode ......................................... C0.3 v to 6 v temp .................. C0.3 v to lesser of ( v cc + 0.3 v ) or 6 v i pgood _ all ............................................................... 5 ma (note 1) 13 14 15 16 top view 39 gnd uhf package 38-lead (5mm 7mm) plastic qfn 17 18 19 38 37 36 35 34 33 32 24 25 26 27 28 29 30 31 8 7 6 5 4 3 2 1fb1 v in1 sw1 sw2 v in2 fb2 fb3 v in3 sw3 sw4 v in4 fb4 fb8 v in8 sw8 sw7 v in7 fb7 fb6 v in6 sw6 sw5 v in5 fb5 en1 en2 temp v cc mode en7 en8 en4 en3 pgood_all sync rt en6 en5 23 22 21 20 9 10 11 12 t jmax = 150c, v ja = 34c/w exposed pad (pin 39) is gnd, must be soldered to pcb 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 top view fe package 38-lead plastic tssop 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 temp en2 en1 fb1 v in1 sw1 sw2 v in2 fb2 fb3 v in3 sw3 sw4 v in4 fb4 en4 en3 pgood_all sync v cc mode en7 en8 fb8 v in8 sw8 sw7 v in7 fb7 fb6 v in6 sw6 sw5 v in5 fb5 en5 en6 rt 39 gnd t jmax = 150c, v ja = 25c/w exposed pad (pin 39) is gnd, must be soldered to pcb order information lead free finish tape and reel part marking* package description temperature range ltc3374euhf#pbf ltc3374euhf#trpbf 3374 38-lead (5mm w 7mm) plastic qfn C40c to 125c ltc3374iuhf #pbf ltc3374iuhf#trpbf 3374 38-lead (5mm w 7mm) plastic qfn C40c to 125c ltc3374huhf #pbf ltc3374huhf#trpbf 3374 38-lead (5mm w 7mm) plastic qfn C40c to 150c ltc3374efe #pbf ltc3374efe#trpbf ltc3374efe 38-lead plastic tssop C40c to 125c ltc3374 ifef #pbf ltc3374ifef#trpbf ltc3374ife 38-lead plastic tssop C40c to 125c ltc3374hfe #pbf ltc3374hfe#trpbf ltc3374hfe 38-lead plastic tssop C40c to 150c consult lt c marketing for parts specified with wider operating temperature ranges. *the temperature grade is identified by a label on the shipping container. consult lt c marketing for information on nonstandard lead based finish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ operating junction temperature range ( notes 2, 3) ............................................ C40 c to 150 c storage temperature range .................. C65 c to 150 c
ltc 3374 4 3374f for more information www.linear.com/ltc3374 the l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at t a = 25c (note 2). v cc = v in1-8 = 3.3v, unless otherwise specified. electrical characteristics symbol parameter conditions min typ max units v vcc v cc voltage range l 2.7 5.5 v v vcc_uvlo undervoltage threshold on v cc v cc voltage falling v cc voltage rising l l 2.35 2.45 2.45 2.55 2.55 2.65 v v i vcc_alloff v cc input supply current all switching regulators in shutdown 8 18 a i vcc v cc input supply current at least 1 buck active sync = 0v, r t = 400k, v fb_buck = 0.85v sync = 2mhz 45 200 75 275 a a f osc internal oscillator frequency v rt = v cc , sync = 0v v rt = v cc , sync = 0v r rt = 400k, sync = 0v l l 1.8 1.75 1.8 2 2 2 2.2 2.25 2.2 mhz mhz mhz f sync synchronization frequency t low , t high > 40ns 1 3 mhz v sync sync level high sync level low l l 1.2 0.4 v v v rt rt servo voltage r rt = 400k l 780 800 820 mv temperature monitor v temp(room) temp voltage at 25c 150 mv ? v temp /c v temp slope 6.75 mv/c ot overtemperature shutdown temperature rising 165 c ot hyst overtemperature hysteresis 10 c 1a buck regulators v buck buck input voltage range l 2.25 5.5 v v out buck output voltage range v fb v in v v in_uvlo undervoltage threshold on v in v in voltage falling v in voltage rising l l 1.95 2.05 2.05 2.15 2.15 2.25 v v i vin_buck burst mode ? operation forced continuous mode operation shutdown input current shutdown input current v fb_buck = 0.85v (note 4) i sw_buck = 0a, v fb_buck = 0v all switching regulators in shutdown at least one other buck active 18 400 0 1 50 550 1 2 a a a a i fwd pmos current limit (note 5) 2.0 2.3 2.7 a v fb feedback regulation voltage l 780 800 820 mv i fb feedback leakage current v fb_buck = 0.85v C50 50 na dmax maximum duty cycle v fb_buck = 0v l 100 % r pmos pmos on -resistance i sw_buck = 100ma 265 m r nmos nmos on-resistance i sw_buck = 100ma 280 m i leakp pmos leakage current en_buck = 0 C2 2 a i leakn nmos leakage current en_buck = 0 C2 2 a t ss soft-start time 1 ms v pgood( fall) falling pgood threshold voltage 92.5 % v pgood(hys) pgood hysteresis 1 % buck regulators combined i fwd 2 pmos current limit 2 buck converters combined (note 5) 4.6 a i fwd 3 pmos current limit 3 buck converters combined (note 5) 6.9 a i fwd 4 pmos current limit 4 buck converters combined (note 5) 9.2 a
ltc 3374 5 3374f for more information www.linear.com/ltc3374 the l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at t a = 25c (note 2). v cc = v in1-8 = 3.3v, unless otherwise specified. electrical characteristics note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: the ltc3374 is tested under pulsed load conditions such that t j t a . the ltc3374e is guaranteed to meet specifications from 0c to 85c junction temperature. specifications over the C40c to 125c operating junction temperature range are assured by design, characterization and correlation with statistical process controls. the ltc3374i is guaranteed over the C40c to 125c operating junction temperature range and the ltc3374h is guaranteed over the C40c to 150c operating junction temperature range. high junction temperatures degrade operating lifetimes; operating lifetime is derated for junction temperatures greater than 125c. note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. the junction temperature (t j in c) is calculated from ambient temperature (t a in c) and power dissipation (p d in watts) according to the formula: t j = t a + (p d ? ja ) where ja (in c/w) is the package thermal impedance. symbol parameter conditions min typ max units interface logic pins (pbgood_all, mode) i oh output high leakage current pgood_all 5.5v at pin C1 1 a v ol output low voltage pgood_all 3ma into pin 0.1 0.4 v v ih input high threshold mode l 1.2 v v il input low threshold mode l 0.4 v interface logic pins (en1, en2, en3, en4, en5, en6, en7, en8) v hi_alloff enable rising threshold all regulators disabled l 400 730 1200 mv v en_hys enable falling hysteresis 60 mv v hi enable rising threshold at least one regulator enabled l 380 400 420 mv i en enable pin leakage current en = v cc = v in = 5.5v C1 1 a note 3: the ltc3374 includes overtemperature protection which protects the device during momentary overload conditions. junction temperatures will exceed 150c when overtemperature protection is active. continuous operation above the specified maximum operating junction temperature may impair device reliability. note 4: static current, switches not switching. actual current may be higher due to gate charge losses at the switching frequency. note 5: the current limit features of this part are intended to protect the ic from short term or intermittent fault conditions. continuous operation above the maximum specified pin current rating may result in device degradation over time.
ltc 3374 6 3374f for more information www.linear.com/ltc3374 typical performance characteristics v cc supply current vs temperature v cc supply current vs temperature rt programmed oscillator frequency vs temperature default oscillator frequency vs temperature oscillator frequency vs v cc v cc undervoltage threshold vs temperature buck v in undervoltage threshold vs temperature v cc supply current vs temperature temperature (c) ?50 uv threshold (v) 2.50 2.60 150 3374 g01 2.40 2.30 0 50 100 ?25 25 75 125 2.70 2.45 2.55 2.35 2.65 v cc rising v cc falling temperature (c) ?50 uv threshold (v) 2.10 2.20 150 3374 g02 2.00 1.90 0 50 100 ?25 25 75 125 2.30 2.05 2.15 1.95 2.25 v in rising v in falling temperature (c) ?50 i vcc_alloff (a) 30 45 50 150 3374 g03 25 20 0 0 50 100 ?25 25 75 125 10 60 55 40 35 15 5 all regulators in shutdown v cc = 5.5v v cc = 2.7v v cc = 3.3v temperature (c) ?50 i vcc (a) 100 150 3374 g04 50 0 0 50 100 ?25 25 75 125 25 125 75 v cc = 5.5v v cc = 2.7v at least one buck enabled sync = 0v fb = 850mv v cc = 3.3v temperature (c) ?50 f osc (mhz) 1.95 2.10 150 3374 g06 1.85 1.80 0 50 100 ?25 25 75 125 2.20 1.90 2.00 2.05 2.15 v cc = 5.5v v cc = 3.3v v cc = 2.7v r rt = 402k temperature (c) ?50 f osc (mhz) 1.95 2.10 150 3374 g07 1.85 1.80 0 50 100 ?25 25 75 125 2.20 1.90 2.00 2.05 2.15 v cc = 5.5v v cc = 3.3v v cc = 2.7v v rt = v cc v cc (v) 2.7 f osc (mhz) 1.95 2.10 5.5 3374 g08 1.85 1.80 3.5 4.3 5.1 3.1 3.9 4.7 2.20 1.90 2.00 2.05 2.15 v rt = v cc r rt = 402k temperature (c) ?50 i vcc (a) 320 280 150 3374 g05 160 120 0 0 50 100 ?25 25 75 125 80 40 400 360 240 200 v cc = 5.5v v cc = 3.3v v cc = 2.7v at least one buck enabled sync = 2mhz
ltc 3374 7 3374f for more information www.linear.com/ltc3374 oscillator frequency vs r t enable threshold vs temperature v temp vs temperature typical performance characteristics buck v in supply current vs temperature buck v in supply current vs temperature v out vs temperature enable pin precision threshold vs temperature r rt (k) 250 f osc (mhz) 2.0 2.5 3.0 650 750700 3374 g09 1.5 1.0 0 350 450 550 300 800 400 500 600 0.5 4.0 3.5 v cc = 3.3v 0 ?200 v temp (mv) 0 400 1400 800 20 10080 200 1000 1200 600 40 60 120 140 actual v temp ideal v temp temperature (c) 3374 g10 temperature (c) ?50 400 en threshold (mv) 450 550 600 650 900 750 0 50 75 3374 g11 500 800 850 700 ?25 25 100 125 150 all regulators disabled v cc = 3.3v en rising en falling temperature (c) ?50 en threshold (mv) 395 410 150 3374 g12 385 380 0 50 100 ?25 25 75 125 420 390 400 405 415 en rising en falling temperature (c) ?50 i vin_burst (a) 40 150 3374 g13 10 0 1251007550250?25 50 20 30 burst mode operation fb = 850mv v in = 5.5v v in = 2.25v v in = 3.3v temperature (c) ?50 i vin_forced_continuous (a) 450 500 150 3374 g14 50 100 150 0 1251007550250?25 550 200 250 300 350 400 forced continuous mode fb = 0v v in = 5.5v v in = 2.25v v in = 3.3v temperature (c) ?50 v out (v) 1.84 1.86 150 3374 g15 1.72 1251007550250?25 1.88 1.74 1.76 1.78 1.80 1.82 forced continuous mode load = 0ma v in = 5.5v v in = 2.25v v in = 3.3v pmos current limit vs temperature temperature (c) ?50 i fwd (a) 2.5 150 3374 g16 2.1 2.2 2.0 1251007550250?25 2.6 2.3 2.4 v in = 3.3v
ltc 3374 8 3374f for more information www.linear.com/ltc3374 typical performance characteristics 2a buck efficiency vs i load 3a buck efficiency vs i load 3a buck efficiency vs i load 1a buck efficiency vs i load 1a buck efficiency vs i load 2a buck efficiency vs i load load current (ma) 1 40 efficiency (%) 50 60 70 80 10 100 1000 3374 g19 30 20 10 0 90 100 burst mode operation forced continuous mode v out = 1.8v f osc = 2mhz l = 2.2h v in = 2.25v v in = 3.3v v in = 5.5v load current (ma) 1 40 efficiency (%) 50 60 70 80 10 100 1000 3374 g20 30 20 10 0 90 100 burst mode operation forced continuous mode v out = 2.5v f osc = 2mhz l = 2.2h v in = 2.7v v in = 3.3v v in = 5.5v load current (ma) 1 40 efficiency (%) 50 60 70 80 10 100 1000 3374 g21 30 20 10 0 90 100 burst mode operation forced continuous mode v out = 1.8v f osc = 2mhz l = 2.2h v in = 2.25v v in = 3.3v v in = 5.5v load current (ma) 1 40 efficiency (%) 50 60 70 80 10 100 1000 3374 g22 30 20 10 0 90 100 burst mode operation forced continuous mode v out = 2.5v f osc = 2mhz l = 2.2h v in = 2.7v v in = 3.3v v in = 5.5v load current (ma) 1 40 efficiency (%) 50 60 70 80 10 100 1000 3374 g23 30 20 10 0 90 100 burst mode operation forced continuous mode v out = 1.8v f osc = 2mhz l = 2.2h v in = 2.25v v in = 3.3v v in = 5.5v load current (ma) 1 40 efficiency (%) 50 60 70 80 10 100 1000 3374 g24 30 20 10 0 90 100 burst mode operation forced continuous mode v out = 2.5v f osc = 2mhz l = 2.2h v in = 2.7v v in = 3.3v v in = 5.5v pmos r ds(on) vs temperature nmos r ds(on) vs temperature temperature (c) ?50 r ds(on) (m) 550 500 150 3374 g17 250 300 350 200 1251007550250?25 600 400 450 v in = 2.25v v in = 3.3v v in = 5.5v temperature (c) ?50 r ds(on) (m) 550 500 150 3374 g18 250 300 350 200 1251007550250?25 600 400 450 v in = 2.25v v in = 3.3v v in = 5.5v
ltc 3374 9 3374f for more information www.linear.com/ltc3374 4a buck efficiency vs i load 4a buck efficiency vs i load 1a buck efficiency vs frequency (forced continuous mode) typical performance characteristics 1a buck efficiency vs frequency (forced continuous mode) 1a buck efficiency vs i load (across operating frequency) 1a buck regulator load regulation (forced continuous mode) 4a buck regulator load regulation (forced continuous mode) 1a buck regulator line regulation (forced continuous mode) load current (ma) 1 40 efficiency (%) 50 60 70 80 10 100 1000 3374 g25 30 20 10 0 90 100 burst mode operation forced continuous mode v out = 1.8v f osc = 2mhz l = 2.2h v in = 2.25v v in = 3.3v v in = 5.5v load current (ma) 1 40 efficiency (%) 50 60 70 80 10 100 1000 3374 g26 30 20 10 0 90 100 burst mode operation forced continuous mode v out = 2.5v f osc = 2mhz l = 2.2h v in = 2.7v v in = 3.3v v in = 5.5v frequency (mhz) 1 efficiency (%) 60 80 100 2.6 3374 g27 40 20 50 70 90 30 10 0 1.4 1.8 2.2 1.2 2.8 1.6 2 2.4 3 v in = 5.5v v in = 3.3v v in = 2.25v v out = 1.8v i l = 100ma f osc = 2mhz l = 3.3h frequency (mhz) 1 efficiency (%) 60 80 100 2.6 3374 g28 40 20 50 70 90 30 10 0 1.4 1.8 2.2 1.2 2.8 1.6 2 2.4 3 i l = 100ma i l = 500ma i l = 20ma v out = 1.8v v in = 3.3v f osc = 2mhz l = 3.3h load current (ma) 1 40 efficiency (%) 50 60 70 80 10 100 1000 3374 g29 30 20 10 0 90 100 burst mode operation forced continuous mode v out = 1.8v v in = 3.3v f osc = 1mhz l = 3.3h f osc = 2mhz l = 2.2h f osc = 3mhz l = 1h v in = 5.5v dropout v in = 3.3v v in = 2.25v i l (ma) 1 v out (v) 1.800 1.812 1000 3374 g30 1.792 1.788 1.784 1.780 100 10 1.820 1.796 1.804 1.808 1.816 f osc = 2mhz l = 2.2h v in = 5.5v v in = 3.3v v in = 2.25v i l (ma) 1 v out (v) 1.800 1.812 1000 3374 g31 1.792 1.788 1.784 1.780 100 10 1.820 1.796 1.804 1.808 1.816 f osc = 2mhz l = 2.2h dropout i l = 100ma i l = 500ma v in (v) 2.25 2.75 v out (v) 1.810 5.25 4.25 4.75 3374 g32 1.790 1.785 1.780 3.753.25 1.820 1.795 1.800 1.805 1.815 f osc = 2mhz l = 2.2h
ltc 3374 10 3374f for more information www.linear.com/ltc3374 typical performance characteristics 1a buck regulator, transient response (forced continuous mode) 4a buck regulator, transient response (forced continuous mode) 4a buck regulator, transient response (burst mode operation) v out 100mv/div ac-coupled 0ma 50s/div load step = 100ma to 700ma v in = 3.3v v out = 1.8v 3374 g36 inductor current 200ma/div v out 100mv/div ac-coupled 0ma 50s/div load step = 400ma to 2.8a v in = 3.3v v out = 1.8v 3374 g37 inductor current 1a/div v out 100mv/div ac-coupled 0ma 50s/div load step = 400ma to 2.8a v in = 3.3v v out = 1.8v 3374 g38 inductor current 1a/div 1 a buck regulator no-load start-up transient (burst mode operation) 4a buck regulator no-load start-up transient (forced continuous mode) 1a buck regulator, transient response (burst mode operation) v out 500mv/div en 2v/div 200s/div v in = 3.3v 3374 g33 inductor current 500ma/div v out 500mv/div en 2v/div 200s/div v in = 3.3v 3374 g34 inductor current 500ma/div v out 100mv/div ac-coupled 0ma 50s/div load step = 100ma to 700ma v in = 3.3v v out = 1.8v 3374 g35 inductor current 200ma/div
ltc 3374 11 3374f for more information www.linear.com/ltc3374 pin functions (qfn/tssop) fb 1 ( pin 1/ pin 4): buck regulator 1 feedback pin . receives feedback by a resistor divider connected across the output . v in1 (pin 2/pin 5): buck regulator 1 input supply. bypass to gnd with a 10f or larger ceramic capacitor. sw1 ( pin 3/ pin 6): buck regulator 1 switch node . external inductor connects to this pin. sw2 ( pin 4/ pin 7): buck regulator 2 switch node . external inductor connects to this pin. v in2 (pin 5/pin 8): buck regulator 2 input supply. bypass to gnd with a 10f or larger ceramic capacitor. may be driven by an independent supply or must be shorted to v in 1 when buck regulator 2 is combined with buck regulator 1 for higher current. fb 2 ( pin 6/ pin 9): buck regulator 2 feedback pin . receives feedback by a resistor divider connected across the output . connecting fb2 to v in2 combines buck regulator 2 with buck regulator 1 for higher current. up to four converters may be combined in this way. fb3 (pin 7/pin 10): buck regulator 3 feedback pin. receives feedback by a resistor divider connected across the output. connecting fb3 to v in3 combines buck regula- tor ?3 with buck regulator 2 for higher current. up to four converters may be combined in this way. v in3 ( pin 8/ pin 11): buck regulator 3 input supply . bypass to gnd with a 10f or larger ceramic capacitor. may be driven by an independent supply or must be shorted to v in 2 when buck regulator 3 is combined with buck regulator 2 for higher current. sw3 (pin 9/pin 12): buck regulator 3 switch node. external inductor connects to this pin. sw4 (pin 10/pin 13): buck regulator 4 switch node. external inductor connects to this pin. v in4 ( pin 11/pin 14): buck regulator 4 input supply. bypass to gnd with a 10f or larger ceramic capacitor. may be driven by an independent supply or must be shorted to v in3 when buck regulator 4 is combined with buck regulator 3 for higher current. fb4 (pin 12/pin 15): buck regulator 4 feedback pin. receives feedback by a resistor divider connected across the output. connecting fb4 to v in4 combines buck regula - tor 4 with buck regulator 3 for higher current. up to four converters may be combined in this way. en4 (pin 13/pin 16): buck regulator 4 enable input. active high. en3 (pin 14/pin 17): buck regulator 3 enable input. active high. pgood_all (pin 15/pin 18): pgood status pin. open- drain output. when the regulated output voltage of any enabled switching regulator is more than 7.5% below its programmed level, this pin is driven low. when all buck regulators are disabled pgood_all is driven low. sync ( pin 16/pin 19): oscillator synchronization pin. driv- ing sync with an external clock signal will synchronize all switchers to the applied frequency . the slope compensation is automatically adapted to the external clock frequency. the absence of an external clock signal will enable the frequency programmed by the rt pin. sync should be held at ground if not used. do not float. rt (pin 17/pin 20): oscillator frequency pin. this pin provides two modes of setting the switching frequency. connecting a resistor from rt to ground will set the switch - ing frequency based on the resistor value. if rt is tied to v cc the internal 2mhz oscillator will be used. do not float. en6 (pin 18/pin 21): buck regulator 6 enable input. active high. en5 (pin 19/pin 22): buck regulator 5 enable input. active high. fb5 (pin 20/pin 23): buck regulator 5 feedback pin. receives feedback by a resistor divider connected across the output. connecting fb5 to v in5 combines buck regula- tor 5 with buck regulator 4 for higher current. up to four converters may be combined in this way.
ltc 3374 12 3374f for more information www.linear.com/ltc3374 pin functions (qfn/tssop) v in5 ( pin 21/pin 24): buck regulator 5 input supply. bypass to gnd with a 10f or larger ceramic capacitor. may be driven by an independent supply or must be shorted to v in4 when buck regulator 5 is combined with buck regulator 4 for higher current. sw5 (pin 22/pin 25): buck regulator 5 switch node. external inductor connects to this pin. sw6 (pin 23/pin 26): buck regulator 6 switch node. external inductor connects to this pin. v in6 ( pin 24/pin 27): buck regulator 6 input supply. bypass to gnd with a 10f or larger ceramic capacitor. may be driven by an independent supply or must be shorted to v in5 when buck regulator 6 is combined with buck regulator 5 for higher current. fb6 (pin 25/pin 28): buck regulator 6 feedback pin. receives feedback by a resistor divider connected across the output. connecting fb6 to v in6 combines buck regula- tor 6 with buck regulator 5 for higher current. up to four converters may be combined in this way. fb7 (pin 26/pin 29): buck regulator 7 feedback pin. receives feedback by a resistor divider connected across the output. connecting fb7 to v in7 combines buck regula- tor 7 with buck regulator 6 for higher current. up to four converters may be combined in this way. v in7 ( pin 27/pin 30): buck regulator 7 input supply. bypass to gnd with a 10f or larger ceramic capacitor. may be driven by an independent supply or must be shorted to v in6 when buck regulator 7 is combined with buck regulator 6 for higher current. sw7 (pin 28/pin 31): buck regulator 7 switch node. external inductor connects to this pin. sw8 (pin 29/pin 32): buck regulator 8 switch node . external inductor connects to this pin. v in8 ( pin 30/pin 33): buck regulator 8 input supply. bypass to gnd with a 10f or larger ceramic capacitor. may be driven by an independent supply or must be shorted to v in7 when buck regulator 8 is combined with buck regulator 7 for higher current. fb8 (pin 31/pin 34): buck regulator 8 feedback pin. receives feedback by a resistor divider connected across the output . connecting fb8 to v in8 combines buck regula- tor 8 with buck regulator 7 for higher current. up to four converters may be combined in this way. en8 (pin 32/pin 35): buck regulator 8 enable input. active high. en7 (pin 33/pin 36): buck regulator 7 enable input. active high. mode (pin 34/pin 37): logic input. mode enables burst mode functionality for all the buck switching regulators when the pin is set low. when the pin is set high, all the buck switching regulators will operate in forced continu- ous mode. v cc (pin 35/pin 38): internal bias supply. bypass to gnd with a 10f or larger ceramic capacitor. temp (pin 36/pin 1): temperature indication pin. temp outputs a voltage of 150mv (typical) at room tempera- ture. the temp voltage will change by 6.75mv/c (typical) giving an external indication of the ltc3374 internal die temperature. en2 (pin 37/pin 2): buck regulator 2 enable input. active high. en1 (pin 38/pin 3): buck regulator 1 enable input. active high. gnd (exposed pad pin 39/exposed pad pin 39): ground. the exposed pad must be connected to a continuous ground plane on the printed circuit board directly under the ltc3374 for electrical contact and rated thermal performance .
ltc 3374 13 3374f for more information www.linear.com/ltc3374 block diagram (pin numbers reflect qfn package) 13 39 en4 12 fb4 10 sw4 11 v in4 14 en3 7 fb3 9 sw3 8 v in3 37 en2 6 fb2 4 sw2 master/slave lines master/slave lines master/slave lines master/slave lines gnd (exposed pad) master/slave lines master/slave lines master/slave lines 5 v in2 38 en1 1 fb1 3 sw1 ref, clk 8 pgood 2 19 20 22 21 18 25 23 24 33 26 28 27 32 31 29 30 v in1 en5 3374 bd fb5 sw5 v in5 en6 fb6 sw6 v in6 en7 fb7 sw7 v in7 en8 fb8 sw8 v in8 34 mode pgood_all buck regulator 4 1a buck regulator 3 1a buck regulator 2 1a buck regulator 1 1a buck regulator 5 1a buck regulator 6 1a buck regulator 7 1a buck regulator 8 1a bandgap, oscillator, uv, ot temp monitor top logic 17 rt 16 sync 36 temp 35 v cc 15
ltc 3374 14 3374f for more information www.linear.com/ltc3374 operation buck switching regulators the ltc3374 contains eight monolithic 1a synchronous buck switching regulators. all of the switching regula- tors are internally compensated and need only external feedback resistors to set the output voltage. the switch- ing regulators offer two operating modes: burst mode operation (when the mode pin is set low) for higher efficiency at light loads and forced continuous pwm mode (when the mode pin is set high) for lower noise at light loads. the mode pin collectively sets the operating mode for all enabled buck switching regulators. in burst mode operation at light loads, the output capacitor is charged to a voltage slightly higher than its regulation point. the regulator then goes into sleep mode, during which time the output capacitor provides the load current. in sleep most of the regulators circuitry is powered down, helping conserve input power. when the output capacitor droops below its programmed value, the circuitry is powered on and another burst cycle begins. the sleep time decreases as load current increases. in burst mode operation, the regulator will burst at light loads whereas at higher loads it will operate at constant frequency pwm mode operation. in forced continuous mode, the oscillator runs continu- ously and the buck switch currents are allowed to reverse under very light load conditions to maintain regulation. this mode allows the buck to run at a fixed frequency with minimal output ripple. each buck switching regulator has its own v in , sw, fb and en pins to maximize flexibility. the enable pins have two different enable threshold voltages that depend on the operating state of the ltc3374. with all regulators disabled, the enable pin threshold is set to 730mv ( typical ). once any regulator is enabled, the enable pin thresholds of the remaining regulators are set to a bandgap-based 400mv and the en pins are each monitored by a precision comparator. this precision en threshold may be used to provide event-based sequencing via feedback from other previously enabled regulators. all buck regulators have forward and reverse-current limiting, soft-start to limit inrush current during start - up , and short - circuit protection . figure 1. buck regulators configured as master-slave buck regulator 1 (master) v in v in v in sw1 c out v out 1.2v 2a 400k l1 800k fb1 en1 buck regulator 2 (slave) sw2 en2 v in1 v in2 fb2 3374 f01 the buck switching regulators are phased in 90 steps to reduce noise and input ripple. the phase step determines the fixed edge of the switching sequence, which is when the pmos turns on. the pmos off (nmos on) phase is subject to the duty cycle demanded by the regulator. bucks 1 and 2 are set to 0, bucks 3 and 4 are set to 90, bucks 5 and 6 are set to 180, and bucks 7 and 8 are set to 270. in shutdown all sw nodes are high impedance. the buck regulator enable pins may be tied to v out volt- ages, through a resistor divider, to program power-up sequencing. buck regulators with combined power stages up to four adjacent buck regulators may be combined in a master-slave configuration by connecting their sw pins together, connecting their v in pins together, and connecting the higher numbered bucks fb pin(s) to the input supply. the lowest numbered buck is always the master. in figure ?1, buck regulator 1 is the master. the feedback network connected to the fb1 pin programs the output voltage to 1.2v. the fb2 pin is tied to v in1-2 , which configures buck regulator 2 as the slave. the sw1 and sw2 pins must be tied together, as must the v in1 and v in2 pins. the slave buck control circuitry draws no current. the enable of the master buck (en1) controls the
ltc 3374 15 3374f for more information www.linear.com/ltc3374 operation of the combined bucks; the enable of the slave regulator (en2) must be tied to ground. any combination of 2, 3, or 4 adjacent buck regulators may be combined to provide either 2a, 3a, or 4a of aver - age output load current. for example, buck regulator 1 and buck regulator 2 may run independently, while buck regulators 3 and 4 may be combined to provide 2a, while buck regulators 5 through 8 may be combined to provide 4a. buck regulator 1 is never a slave, and buck regulator 8 is never a master. 15 unique output power stage con- figurations are possible to maximize application flexibility. power failure reporting via pgood_all pin power failure conditions are reported back via the pgood_all pin. all buck switching regulators have an internal power good ( pgood ) signal . when the regulated output voltage of an enabled switcher rises above 93.5% of its programmed value , the pgood signal will transition high. when the regulated output voltage falls below 92.5% of its programmed value, the pgood signal is pulled low. if any internal pgood signal stays low for greater than 100s, then the pgood_all pin is pulled low, indicating to a microprocessor that a power failure fault has occurred. the 100s filter time prevents the pin from being pulled low due to a transient. an error condition that pulls the pgood_all pin low is not latched. when the error condition goes away, the pgood_all pin is released and is pulled high if no other error condition exists. if no buck switching regulators are enabled, then pgood_all will be pulled low. temperature monitoring and overtemperature protection to prevent thermal damage to the ltc3374 and its sur - rounding components , the ltc 3374 incorporates an overtemperature (ot) function. when the ltc3374 die temperature reaches 165c (typical) all enabled buck switching regulators are shut down and remain in shutdown until the die temperature falls to 155c (typical). operation the temperature may be read back by the user by sampling the temp pin analog voltage . the temperature , t , indicated by the temp pin voltage is given by: t = v temp + 19mv 6.75mv ? 1 c (1) if temperature monitoring functionality is not desired , then the user may shut down the temperature monitor in order to lower quiescent current (15a typical) by tying temp to v cc . in this case all enabled buck switching regulators are still shut down when the die temperature reaches 165c (typical) and remain in shutdown until the die tempera- ture falls to 155c (typical). if none of the buck switching regulators are enabled, then the temperature monitor is also shut down to further reduce quiescent current. programming the operating frequency selection of the operating frequency is a trade-off between efficiency and component size. high frequency operation allows the use of smaller inductor and capacitor values. operation at lower frequencies improves efficiency by reducing internal gate charge losses but requires larger inductance values and/or capacitance to maintain low output voltage ripple. the operating frequency for all of the ltc3374 regulators is determined by an external resistor that is connected between the rt pin and ground. the operating frequency can be calculated by using the following equation: f osc = 8 ? 10 11 ? ? hz r t (2) while the ltc3374 is designed to function with operat- ing frequencies between 1mhz and 3mhz, it has safety clamps that will prevent the oscillator from running faster than 4mhz (typical) or slower than 250khz (typical). tying the rt pin to v cc sets the oscillator to the default internal operating frequency of 2mhz (typical).
ltc 3374 16 3374f for more information www.linear.com/ltc3374 operation the ltc3374s internal oscillator can be synchronized through an internal pll circuit , to an external frequency by applying a square wave clock signal to the sync pin. during synchronization, the top mosfet/turn-on of buck switching regulators 1 and 2 are locked to the rising edge of the external frequency source . all other buck switching regulators are locked to the appropriate phase of the ex- ternal frequency source (see buck switching regulators). the synchronization frequency range is 1mhz to 3mhz. after detecting an external clock on the first rising edge of the sync pin, the pll starts up at the current frequency being programmed by the rt pin. the internal pll then requires a certain number of periods to gradually settle until the frequency at sw matches the frequency and phase of sync. when the external clock is removed the ltc3374 needs approximately 5s to detect the absence of the external clock. during this time, the pll will continue to provide clock cycles before it recognizes the lack of a sync input. once the external clock removal has been identified, the oscillator will gradually adjust its operating frequency to match the desired frequency programmed at the rt pin. sync should be connected to ground if not used.
ltc 3374 17 3374f for more information www.linear.com/ltc3374 applications information buck switching regulator output voltage and feedback network the output voltage of the buck switching regulators is programmed by a resistor divider connected from the switching regulators output to its feedback pin and is given by v out = v fb (1 + r2/r1) as shown in figure 2. typical values for r1 range from 40k to 1m. the buck regulator transient response may improve with optional capacitor c ff that helps cancel the pole created by the feedback resistors and the input capacitance of the fb pin. experimentation with capacitor values between 2pf and 22pf may improve transient response. figure 2. feedback components buck switching regulator v out c out (optional) c ff r2 r1 fb 3374 f02 + buck regulators all eight buck regulators are designed to be used with inductors ranging from 1h to 3.3h depending on the lowest switching frequency that the buck regulator must operate at. to operate at 1mhz a 3.3h inductor should be used, while to operate at 3mhz a 1h inductor may be used. table 1 shows some recommended inductors for the buck regulators. the input supply needs to be decoupled with a 10f capacitor while the output needs to be decoupled with a 22f capacitor. refer to the capacitor selection section for details on selecting a proper capacitor. combined buck regulators a single 2a buck regulator is available by combining two adjacent 1a buck regulators together. likewise a 3a or 4a buck regulator is available by combining any three or four adjacent buck regulators respectively. tables 2, 3, and 4 show recommended inductors for these configurations. the input supply needs to be decoupled with a 22 f capaci - tor while the output needs to be decoupled with a 47f capacitor for a 2a combined buck regulator. likewise for 3a and 4a configurations the input and output capacitance must be scaled up to account for the increased load. refer to the capacitor selection section for details on selecting a proper capacitor. in many cases, any extra unused buck converters may be used to increase the efficiency of the active regulators. in general the efficiency will improve for any regulators running close to their rated load currents. if there are unused regulators, the user should look at their specific applications and current requirements to decide whether to add extra stages. input and output decoupling capacitor selection the ltc3374 has individual input supply pins for each buck switching regulator and a separate v cc pin that supplies power to all top level control and logic. each of these pins must be decoupled with low esr capacitors to gnd. these capacitors must be placed as close to the pins as possible. ceramic dielectric capacitors are a good compromise between high dielectric constant and stability versus temperature and dc bias. note that the capacitance of a capacitor deteriorates at higher dc bias. it is important to consult manufacturer data sheets and obtain the true capacitance of a capacitor at the dc bias voltage it will be operated at. for this reason, avoid the use of y5v dielectric capacitors. the x5r/x7r dielectric capacitors offer good overall performance. the input supply voltage pins 2/5, 5/8, 8/11, 11/14, 21/24, 24/27, 27/30, 30/33, and 35/38 (qfn/tssop packages) all need to be decoupled with at least 10f capacitors. pcb considerations when laying out the printed circuit board, the following list should be followed to ensure proper operation of the ltc3374: 1. the exposed pad of the package ( pin 39) should connect directly to a large ground plane to minimize thermal and electrical impedance.
ltc 3374 18 3374f for more information www.linear.com/ltc3374 applications information table 1. recommended inductors for 1a buck regulators part number l (h) max i dc (a) max dcr (m) size in mm (l w h) manufacturer ihlp1212aber1r0m-11 1.0 3 38 3 3.6 1.2 vishay 1239as-h-1r0n 1 2.5 65 2.5 2.0 1.2 toko xfl4020-222me 2.2 3.5 23.5 4 4 2.1 coilcraft 1277as-h-2r2n 2.2 2.6 84 3.2 2.5 1.2 toko ihlp1212bzer2r2m-11 2.2 3 46 3 3.6 1.2 vishay xfl4020-332me 3.3 2.8 38.3 4 4 2.1 coilcraft ihlp1212bzer3r3m-11 3.3 2.7 61 3 3.6 1.2 vishay table 2. recommended inductors for 2a buck regulators part number l (h) max i dc (a) max dcr (m) size in mm (l w h) manufacturer xfl4020-102me 1.0 5.1 11.9 4 4 2.1 coilcraft 74437324010 1 9 27 4.45 4.06 1.8 wurth elektronik xal4020-222me 2.2 5.6 38.7 4 4 2.1 coilcraft fdv0530-2r2m 2.2 5.3 15.5 6.2 5.8 3 toko ihlp2020bzer2r2m-11 2.2 5 37.7 5.49 5.18 2 vishay xal4030-332me 3.3 5.5 28.6 4 4 3.1 coilcraft fdv0530-3r3m 3.3 4.1 34.1 6.2 5.8 3 toko table 3. recommended inductors for 3a buck regulators part number l (h) max i dc (a) max dcr (m) size in mm (l w h) manufacturer xal4020-102me 1.0 8.7 14.6 4 4 2.1 coilcraft fdv0530-1r0m 1 8.4 11.2 6.2 5.8 3 toko xal5030-222me 2.2 9.2 14.5 5.28 5.48 3.1 coilcraft ihlp2525czer2r2m-01 2.2 8 20 6.86 6.47 3 vishay 74437346022 2.2 6.5 20 7.3 6.6 2.8 wurth elektonik xal5030-332me 3.3 8.7 23.3 5.28 5.48 3.1 coilcraft spm6530t-3r3m 3.3 7.3 27 7.1 6.5 3 tdk table 4. recommended inductors for 4a buck regulators part number l (h) max i dc (a) max dcr (m) size in mm (l w h) manufacturer xal5030-122me 1.2 12.5 9.4 5.28 5.48 3.1 coilcraft spm6530t-1r0m120 1 14.1 7.81 7.1 6.5 3 tdk xal5030-222me 2.2 9.2 14.5 5.28 5.48 3.1 coilcraft spm6530t-2r2m 2.2 8.4 19 7.1 6.5 3 tdk ihlp2525ezer2r2m -01 2.2 13.6 20.9 6.86 6.47 5 vishay xal6030-332me 3.3 8 20.81 6.36 6.56 3.1 coilcraft fdve1040-3r3m 3.3 9.8 10.1 11.2 10 4 toko
ltc 3374 19 3374f for more information www.linear.com/ltc3374 applications information 2. all the input supply pins should each have a decoupling capacitor. 3. the connections to the switching regulator input supply pins and their respective decoupling capacitors should be kept as short as possible. the gnd side of these capacitors should connect directly to the ground plane of the part. these capacitors provide the ac current to the internal power mosfets and their drivers. it is important to minimize inductance from these capacitors to the v in pins of the ltc 3374. 4. the switching power traces connecting sw1, sw2, sw 3, sw4, sw5, sw6, sw7, and sw8 to their respective inductors should be minimized to reduce radiated emi and parasitic coupling. due to the large voltage swing of the switching nodes, high input impedance sensitive nodes, such as the feedback nodes, should be kept far away or shielded from the switching nodes or poor performance could result. 5. the gnd side of the switching regulator output capaci- tors should connect directly to the thermal ground plane of the part. minimize the trace length from the output capacitor to the inductor(s)/pin(s). 6. in a combined buck regulator application the trace length of switch nodes to the inductor must be kept equal to ensure proper operation. figure 3. detailed front page application ltc3374 exposed pad 2.2h v in1 sw1 fb1 v in8 sw8 fb8 3374 f03 2.2h 806k 649k 1.02m 324k 10f 3.3v to 5.5v 1.8v 1a 3.3v 1a 22f 22f 10f 2.25v to 5.5v 2.2h v in2 sw2 fb2 v in7 sw7 fb7 2.2h 715k 806k 1.0m 365k 10f 3.0v to 5.5v 1.5v 1a 3.0v 1a 22f 22f 10f 2.25v to 5.5v 2.2h v in3 sw3 fb3 v in6 sw6 fb6 2.2h 232k 464k 1.02m 475k 10f 2.5v to 5.5v 1.2v 1a 2.5v 1a 22f 22f 10f 2.25v to 5.5v 2.2h v in4 sw4 fb4 402k rt en1 en2 en3 en4 en5 en6 en7 en8 sync mode v in5 sw5 fb5 v cc pgood_all temp microprocessor control 2.2h 255k 1.02m 1.0m 665k 10f 2.25v to 5.5v 1.0v 1a 2.0v 1a 22f 22f 2.7v to 5.5v microprocessor control 10f 2.25v to 5.5v 10f
ltc 3374 20 3374f for more information www.linear.com/ltc3374 applications information figure 4. buck regulators with sequenced start-up driven from a high voltage upstream buck converter ltc3374 exposed pad 2.2h v in1 sw1 fb1 v in8 sw8 fb8 3374 f04 2.2h 324k 649k 324k 1m 649k 10f 1.2v 1a 2.5v 1a 1.8v 1a 1.6v 1a 1.2v 1a 10f 10f 10f 10f 10f 10f 10f 22f 22f 22f 22f 2.5v 1a 1.8v 1a 1.6v 1a 22f 22f 22f 22f 2.2h v in2 sw2 fb2 v in7 sw7 fb7 2.2h 665k 309k 665k 309k 2.2h v in3 sw3 fb3 v in6 sw6 fb6 2.2h 590k 475k 590k 475k 2.2h v in4 sw4 fb4 402k rt en1 en2 en3 en4 en5 en6 en7 en8 v in5 sw5 fb5 v cc pgood_all temp 2.2h 511k 511k 511k 511k microprocessor control 10f sync mode 0.1f c in 22f v in 5.5v to 36v intv cc 34.8k 470pf 100k 100k mtop, mbot: si7850dp l1 coilcraft ser1360-802kl c out : sanyo 10tpe330m d1: dfls1100 19.1k 2.2f d1 0.1f freq ith sgnd sgnd ltc3891 v in pgood pllin/mode i lim intv cc pgnd l1 8h r sense 7m boost sw bg sense + sense ? extv cc v fb tg mtop mbot 1nf c out 330f 5v 6a track/ss run v in en kill int pb tmr gnd on ltc2955ts8-1 microprocessor control microprocessor control
ltc 3374 21 3374f for more information www.linear.com/ltc3374 applications information figure 5. combined buck regulators with common input supply ltc3374 exposed pad 2.2h v in1 sw1 sw2 sw3 sw4 fb1 v in6 sw8 sw7 sw6 fb6 3374 f05 2.2h 324k 649k 665k 309k 1.2v 3a 2.5v 4a 2.7v to 5.5v 100f 68f 10f 10f 10f 10f 10f 10f 10f 10f v in2 fb2 v in7 fb7 v in3 fb3 v in8 fb8 2.2h v in4 fb4 402k rt en2 en3 en4 en7 en8 en1 en5 en6 sync mode v in5 sw5 fb5 pgood_all temp v cc microprocessor control 511k 511k 1.6v 1a 22f 10f microprocessor control
ltc 3374 22 3374f for more information www.linear.com/ltc3374 package description please refer to http://www .linear.com/designtools/packaging/ for the most recent package drawings. 5.00 0.10 note: 1. drawing conforms to jedec package outline m0-220 variation whkd 2. drawing not to scale 3. all dimensions are in millimeters pin 1 top mark (see note 6) 37 1 2 38 bottom view?exposed pad 5.50 ref 5.15 0.10 7.00 0.10 0.75 0.05 r = 0.125 typ r = 0.10 typ 0.25 0.05 (uh) qfn ref c 1107 0.50 bsc 0.200 ref 0.00 ? 0.05 recommended solder pad layout apply solder mask to areas that are not soldered 3.00 ref 3.15 0.10 0.40 0.10 0.70 0.05 0.50 bsc 5.5 ref 3.00 ref 3.15 0.05 4.10 0.05 5.50 0.05 5.15 0.05 6.10 0.05 7.50 0.05 0.25 0.05 package outline 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.20mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package pin 1 notch r = 0.30 typ or 0.35 45 chamfer uhf package 38-lead plastic qfn (5mm 7mm) (reference ltc dwg # 05-08-1701 rev c)
ltc 3374 23 3374f for more information www.linear.com/ltc3374 information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package description please refer to http://www .linear.com/designtools/packaging/ for the most recent package drawings. 4.75 (.187) ref fe38 (aa) tssop rev c 0910 0.09 ? 0.20 (.0035 ? .0079) 0 ? 8 0.25 ref 0.50 ? 0.75 (.020 ? .030) 4.30 ? 4.50* (.169 ? .177) 1 19 20 ref 9.60 ? 9.80* (.378 ? .386) 38 1.20 (.047) max 0.05 ? 0.15 (.002 ? .006) 0.50 (.0196) bsc 0.17 ? 0.27 (.0067 ? .0106) typ recommended solder pad layout 0.315 0.05 0.50 bsc 4.50 ref 6.60 0.10 1.05 0.10 4.75 ref 2.74 ref 2.74 (.108) millimeters (inches) *dimensions do not include mold flash. mold flash shall not exceed 0.150mm (.006") per side note: 1. controlling dimension: millimeters 2. dimensions are in 3. drawing not to scale see note 4 4. recommended minimum pcb metal size for exposed pad attachment 6.40 (.252) bsc fe package 38-lead plastic tssop (4.4mm) (reference ltc dwg # 05-08-1772 rev c) exposed pad variation aa
ltc 3374 24 3374f for more information www.linear.com/ltc3374 ? linear technology corporation 2013 lt 0513 ? printed in usa related parts typical application part number description comments ltc3589 8-output regulator with sequencing and i 2 c triple i 2 c adjustable high efficiency step-down dc/dc converters: 1.6a, 1a, 1a. high efficiency 1.2a buck-boost dc/dc converter, triple 250ma ldo regulators. pushbutton on/off control with system reset, flexible pin-strap sequencing operation. i 2 c and independent enable control pins, dynamic voltage scaling and slew rate control. selectable 2.25mhz or 1.12mhz switching frequency, 8a standby current, 40-pin 6mm 6mm 0.75mm qfn. ltc3675 7-channel configurable high power pmic four monolithic synchronous buck dc/dcs (1a/1a/500ma/500ma). buck dc/dcs can be paralleled to deliver up to 2 current with a single inductor. independent 1a boost and 1a buck-boost dc/dcs, dual string i 2 c controlled 40v led driver. i 2 c programmable output voltage, operating mode, and switch node slew rate for all dc/dcs. i 2 c read back of dc/dc, led driver, fault status, pushbutton on/off/reset, always-on 25ma ldo. low quiescent current: 16a (all dc/dcs off), 4mm 7mm 0.75mm 44-lead qfn package. ltc3375 8-channel programmable configurable 1a dc/dc 8 1a synchronous buck regulators. can connect up to four power stages in parallel to make a single inductor, high current output (4a maximum), 15 output configurations possible, 7mm 7mm qfn-48 package linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com/ltc3374 ltc3374 exposed pad v in1 10f v in8 fb8 v in6 fb6 v in5 v in4 v in7 v in2 fb2 10f 10f 10f 1h 1h 10f 10f 47f sw7 sw8 sw5 sw6 fb5 rt fb7 v in3 fb3 fb1 sw1 sw2 sw3 10f 10f 68f 47f 1.02m 324k 1h 1.02m 475k 267k 3374 ta02 649k 432k 1h fb4 v cc pgood_all temp sync mode en1 en4 en5 en7 en2 en3 en6 en8 sw4 22f 10f microprocessor control 2.7v to 5.5v 2.25v to 5.5v 2.25v to 5.5v 3.3v to 5.5v 2.5v to 5.5v 3.3v 2a 2.5v 2a 1.2v 1a 2v 3a 324k 649k combined bucks with 3mhz switch frequency and sequenced power up

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