up to 1a output current operating input voltage from 4.4v to 36v 3.3v / ( 2%) / reference voltage output voltage adjustable from 1.2v to 35v low dropout operation: 100% duty cycle 250khz internally fixed frequency voltage feedforward zero load current operation internal current limiting inhibit for zero current consumption sinchronization protection against feedback dis- connection thermal shutdown applications: consumer: stb, dvd, tv, vcr, car radio, lcd monitors networking: xdsl, modems, dc-dc modules computer: printers, audio/graphic cards, optical storage, hard disk drive industrial: chargers, car battery dc-dc converters description the L5970D is a step down monolithic power switching regulator capable to deliver up to 1a at output voltages from 1.2v to 35v. the device uses an internal p-channel d-mos transistor (with a typical rdson of 250m w ) as switching element to minimize the size of the ex- ternal components. an internal oscillator fixes the switching frequency at 250khz. having a minimum input voltage of 4.4v only, it is particularly suitable for 5v bus, available in all computer related applications. pulse by pulse current limit with the internal fre- quency modulation offers an effective constant current short circuit protection. february 2003 ? vin=4.4 to 35v c1 10uf 35v ceramic d1 stps2l25u vcc comp gnd out fb inh sync vref 1 3 7 5 6 4 8 2 r3 4.7k u1 l1 33uh r1 5.6k r2 3.3k c3 22nf 3.3v c4 100uf 10v L5970D vout=3.3v c2 220pf test application circuit so-8 L5970D up to 1a step down switching regulator ordering numbers: L5970D(so-8) L5970D013tr (t&r) 1/10
pins function n. name description 1 out regulator output. 2 sync master/slave synchronization. 3 inh a logical signal (active high) disables the device. if inh not used the pin must be grounded. when it is open an internal pull-up disable the device. 4 comp e/a output for frequency compensation. 5 fb feedback input. connecting directly to this pin results in an output voltage of 1.23v. an external resistive divider is required for higher output voltages. 6v ref 3.3v v ref . no cap is requested for stability. 7 gnd ground. 8v cc unregulated dc input voltage. out sync inh comp 1 3 2 4 vcc vref gnd fb 8 7 6 5 d98in955 pins connection (top view) thermal data symbol parameter value unit r th (j-amb) thermal resistance junction to ambient max. 120 (*) c/w (*) package mounted on board absolute maximum ratings symbol parameter value unit v 8 input voltage 40 v v 1 output dc voltage output peak voltage at t = 0.1 m s -1 to 40 -5 to 40 v v i 1 maximum output current int. limit. v 4 , v 5 analog pins 4 v v 3 inh -0.3v to v cc v 2 sync -0.3 to 4 v p tot power dissipation at t amb 60c 0.75 w t j operating junction temperature range -40 to 150 c t stg storage temperature range -55 to 150 c L5970D 2/10
electrical characteristics (tj = 25c, vcc = 12v, unless otherwise specified.) (*) specification referred to t j from -40 to +125c (1) . symbol parameter test condition min. typ. max. unit v cc operating input voltage range v o = 1.235v; i o = 1a * 4.4 36 v v d dropout voltage v cc = 4.4v; i o = 1a * 0.25 0.5 v i l maximum limiting current v cc = 4.4v to 36v * 1.5 1.87 2.25 a f s switching frequency * 212 250 280 khz 225 250 275 khz duty cycle 0 100 % dynamic characteristics (see test circuit fig. xx note 1). v 5 voltage feedback 4.4v < v cc < 36v, 20ma < i o < 1a 1.220 1.235 1.25 v * 1.198 1.235 1.272 v h efficiency v o = 5v, v cc = 12v 90 % dc characteristics i qop total operating quiescent current *35ma i q quiescent current duty cycle = 0; vfb = 1.5v 2.5 ma i qst-by total stand-by quiescent current v inh > 2.2v v cc = 36v; v inh > 2.2v * * 50 80 100 150 m a m a inhibit inh threshold voltage device on 0.8 v device off 2.2 v error amplifier v oh high level output voltage vfb = 1v 3.5 v v ol low level output voltage vfb = 1.5v 0.4 v i o source source output current v comp = 1.9v; v fb = 1v 200 300 m a i o sink sink output current vcomp = 1.9v; v fb = 1.5v 1 1.5 ma i b source bias current 2.5 4 m a dc open loop gain r l = 50 65 db gm transconductance i comp = -0.1ma to 0.1ma v comp = 1.9v 2.3 ms sync function high input voltage v cc = 4.4v to 36v 2.5 v ref v low input voltage v cc = 4.4v to 36v 0.74 v slave sink current v sync = 0.74v (2) v sync = 2.33v 0.11 0.21 0.25 0.45 ma ma master output amplitude i source = 3ma 2.75 3 v output pulse width no load, v sync = 1.65v 0.20 0.35 m s reference section reference voltage 3.234 3.3 3.366 v i ref = 0 to 5ma v cc = 4.4v to 36v * 3.2 3.3 3.399 v line regulation i ref = 0ma v cc = 4.4v to 36v 510mv load regulation i ref = 0 to 5ma 8 15 mv short circuit current 10 8 30 ma note (1): specification over the -40 to +125 tj temperature range are assured by design, characterization and statistical corre lation. note (2): guaranteed by design. L5970D 3/10
20 30 40 50 60 70 80 90 100 110 120 130 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 io(a) tj(c) vo=3.3v vo=2.5v vo=1.8v vcc=5v ta m b = 25 c figure 1. junction temperature vs. output current (so8) *) *) package mounted on demoboard 20 30 40 50 60 70 80 90 100 110 120 130 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 io(a) tj(c) vo=5v vo=2.5v vo=3.3v vcc=12v tamb=25c figure 2. junction temperature vs. output current (so8) *) 0 20 40 60 80 100 120 140 0.2 0.4 0.6 0.8 1 1.2 1.4 io(a) tj(c) vo=18v vo=12v vo=5v vcc=24v tam b= 25 c figure 3. junction temperature vs. output current (so8) *) 3.276 3.28 3.284 3.288 3.292 3.296 3.3 3.304 3.308 3.312 00.511.5 io (a) vo (v) tj = 125c tj = 25c vcc = 12v vo = 3.3v figure 4. load regulation 3.276 3.28 3.284 3.288 3.292 3.296 3.3 3.304 3.308 3.312 0 1020304 0 vcc (v) tj = 125c tj = 25c vcc = 12v vo = 3.3v vo (v) figure 5. line regulation tj (c) vcc=12v 1.2 1.21 1.22 1.23 1.24 1.25 -50 0 50 100 150 vo (v) vcc = 12v figure 6. output voltage vs. junction temperature L5970D 4/10
1.2 1.4 1.6 1.8 2 -50 050 100 150 tj (c) iq (ma) vcc = 12v dc = 0% figure 7. quiescent current vs. junction temperature 30 40 50 60 70 -50 0 50 100 150 ishd ( m a) vcc = 12v tj (c) figure 8. shutdown current vs.junction temperature 220 230 240 250 260 -50 0 50 100 150 tj (c) fsw (khz) vcc = 12v vo = 3.3v figure 9. switching frequency vs.junction temperature L5970D 5/10
vin = 4.4 to 35v c1 10uf 35v ceramic d1 stps2l25u vcc comp gnd out fb inh sync vref 1 3 7 5 6 4 8 2 r3 4.7k u1 l1 22uh r1 5.6k r2 3.3k c3 22nf 3.3v c4 100uf 10v L5970D vout = 3.3v c2 220pf figure 10. demoboard schematic part list demoboard reference part number description manufacturer c1 10 m f, 25v tokin c4 c1206c221j5gac 220pf, 5%, 50v kemet c3 c1206c223k5rac 22nf, 10%, 50v kemet c2 10tpb100m 100 m f, 10v sanyo r1 5.6k, 1%, 0.25w neohm r2 3.3k, 1%, 0.25w neohm r3 5k, 1%, 0.25w neohm d1 stps2l25u 2a, 25v stmicroelectronics l1 do3316p-333 22 m h, 1.2a coilcraft 75 77 79 81 83 85 87 89 91 93 95 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 io(a) efficiency(%) vo=3.3v vo=2.5v vo=1.8v vcc=5v 75 77 79 81 83 85 87 89 91 93 95 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 io(a) vo=3.3v vo=2.5v vo=1.8v vcc=5v figure 11. efficiency vs. output current 70 72 74 76 78 80 82 84 86 88 90 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 io(a) efficiency(%) vo=5v vo=3.3v vo=2.5v vcc=12v figure 12. efficiency vs. output current L5970D 6/10
42mm 34mm figure 13. pcb layout (component side ) figure 15. pcb layout (front side) figure 14. pcb layout (bottom side) L5970D 7/10
vin=12v c1 10uf 25v ceramic d1 stps25l25u vcc comp gnd out fb inh sync vref L5970D 1 3 7 5 6 4 8 2 r3 4.7k u1 c3 22nf 3.3v vout=3.3v 0.5a c2 220pf vout1=5v 30ma c5 47uf 10v lp=22uh d2 1n4148 c4 100uf 10v n1/n2=2 figure 16. dual output voltage with auxiliary winding application ideas vin=12v c1 10uf 25v ceramic d1 stps2l25u vcc comp gnd out fb inh sync vref 1 3 7 5 6 4 8 2 r3 4.7k u1 l1 33uh 2.7k 24k c4 22nf 3.3v c5 100uf 16v l5970 vout=-12v/0.3a c3 220pf c2 10uf 35v ceramic vin=12v vout=-12v iout=0.5a efficiency=81% figure 17. buck-boost regulator vin=5v c1 10uf 25v ceramic d1 stps2l25u vcc comp gnd out fb inh sync vref l5970 1 3 7 5 6 4 8 2 r3 4.7k u1 l1 33uh 24k 2.7k c3 22nf 3.3v c4 100uf 16v vout=12v/0.3a c2 220pf d2 stps2l25u m1 stn4ne03l vin=5v vout=12v iout=0.3a efficiency=76% figure 18. positive buck-boost regulator vcc gnd out fb inh sync vref 1 3 7 5 6 4 8 2 L5970D comp vcc gnd out fb inh sync vref 1 3 7 5 6 4 8 2 L5970D comp vin figure 19. synchronization example L5970D 8/10
dim. mm inch min. typ. max. min. typ. max. a 1.75 0.069 a1 0.1 0.25 0.004 0.010 a2 1.65 0.065 a3 0.65 0.85 0.026 0.033 b 0.35 0.48 0.014 0.019 b1 0.19 0.25 0.007 0.010 c 0.25 0.5 0.010 0.020 c1 45 (typ.) d (1) 4.8 5.0 0.189 0.197 e 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 3.81 0.150 f (1) 3.8 4.0 0.15 0.157 l 0.4 1.27 0.016 0.050 m 0.6 0.024 s8 (max.) (1) d and f do not include mold flash or protrusions. mold flash or potrusions shall not exceed 0.15mm (.006inch). so8 outline and mechanical data L5970D 9/10
information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsibility for the co nsequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specification mentioned in this pu blication are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectron ics products are not authorized for use as critical components in life support devices or systems without express written approval of stmicr oelectronics. the st logo is a registered trademark of stmicroelectronics ? 2003 stmicroelectronics C printed in italy C all rights reserved stmicroelectronics group of companies australia - brazil - canada - china - finland - france - germany - hong kong - india - israel - italy - japan - malaysia - malt a - morocco - singapore - spain - sweden - switzerland - united kingdom - united states. http://www.st.com L5970D 10/10
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