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up to 1a step down converter operating input voltage from 8v to 55v precise 5.1v reference voltage output voltage adjustable from 0.5v to 50v switching frequency adjustable up to 300khz voltage feedforward zero load current operation internal current limiting (pulse-by- pulse and hiccup mode) protection against feedback dis- connection thermal shutdown description the l4976 is a step down monolithic power switching regulator delivering 1a at a voltage be- tween 3.3v and 50v (selected by a simple exter- nal divider). realized in bcd mixed technology, the device uses an internal power d-mos transis- tor (with a typical rdson of 0.25 w ) to obtain very high efficency and high switching speed. a switching frequency up to 300khz is achiev- able (the maximum power dissipation of the pack- ages must be observed). a wide input voltage range between 8v to 55v and output voltages regulated from 3.3v to 40v cover the majority of todays applications. features of this new generations of dc-dc con- verter include pulse-by-pulse current limit, hiccup mode for short circuit protection, voltage feedfor- ward regulation, protection against feedback loop disconnection and thermal shutdown. the device is available in plastic dual in line, minidip 8 for standard assembly, and so16w for smd assembly. august 2001 ? ordering numbers: l4976 (minidip) l4976d (so16) l4976 1a step down switching regulator minidip so16w 5 2 8 4 1 l4976 c 1 220 m f 63v c 8 330 m f v o =3.3v/1a vi=8v to 55v r 1 20k c 2 2.7nf r 2 9.1k c 4 22nf 3 7 l1 260 m h (77120) 6 d1 gi sb360 c 7 220nf c 6 100nf typical application circuit 1/11
pin functions dip so (*) name function 1 2 gnd ground 2 3 vref 5.1v reference voltage with 20ma current capability. 3 4 osc an external resistor connected between the unregulated input voltage and this pin and a capacitor connected from this pin to ground fix the switching frequency. (line feed forward is automatically obtained) 4 5, 6 out stepdown regulator output 511 v cc unregulated dc input voltage 6 12 boot a capacitor connected between this pin and out allows to drive the internal vdmos 7 13 comp e/a output to be used for frequency compensation 8 14 fb stepdown feedback input. connecting directly to this pin results in an output voltage of 3.3v. an external resistive divider is required for higher output voltages. (*) pins 1, 7, 8, 9, 10, 15 and 16 are not internally, electrically connected to the die. pin connections gnd v ref osc out 1 3 2 4 vcc boot comp fb 8 7 6 5 n.c. gnd v ref osc out n.c. out n.c. n.c. n.c. boot vcc comp fb n.c. n.c. 1 3 2 4 5 6 7 8 14 13 12 11 10 9 15 16 v ref voltages monitor thermal shutdown e/a pwm 3.3v oscillator r s q internal reference 5.1v drive cboot charge cboot charge at light loads 2 7 8 fb comp 3 1 4 6 5 boot osc gnd out v cc 3.3v v ref block diagram minidip so16w l4976 2/11
electrical characteristics (tj = 25c, cosc = 2.7nf, rosc = 20k w , v cc = 24v, unless other- wise specified.) * specification refered to tj from 0 to 125c symbol parameter test condition min. typ. max. unit dynamic characteristic v i operating input voltage range v o = 3.3 to 50v; i o = 1a * 8 55 v v o output voltage i o = 0.5a 3.33 3.36 3.39 v i o = 0.2 to 1a 3.292 3.36 3.427 v v cc = 8 to 55v * 3.22 3.36 3.5 v v d dropout voltage v cc = 10v; i o = 1a 0.44 0.55 v *0.88v i l maximum limiting current v cc = 8 to 55v * 1.5 2 2.5 a efficiency v o = 3.3v; i o = 1a 85 % f s switching frequency * 90 100 110 khz svrr supply voltage ripple rejection v i = v cc +2v rms ; v o = v ref ; i o = 1.a; f ripple = 100hz 60 db voltage stability of switching frequency vcc = 8 to 55v 3 6 % temp. stability of switching frequency t j = 0 to 125c 4 % thermal data symbol parameter minidip so16 unit r th(j-amb) thermal resistance junction to ambient max. 90 (*) 110 (*) c/w (*) package mounted on board. operating temperature rating symbol parameter value unit t j junction temperature range -40 to 150 c absolute maximum ratings symbol parameter value unit minidip s016 v 5 v 11 input voltage 58 v v 4 v 5 ,v 6 output dc voltage output peak voltage at t = 0.1 m s f=200khz -1 -5 v v i 4 i 5 ,i 6 maximum output current int. limit. v 6 -v 5 v12-v 11 14 v v 6 v 12 bootstrap voltage 70 v v 7 v 13 analogs input voltage (v cc = 24v) 12 v v 8 v 14 (v cc = 20v) 6 -0.3 v v p tot power dissipation a t amb 60 c minidip 1w so16 0.8 w t j ,t stg junction and storage temperature -40 to 150 c l4976 3/11
symbol parameter test condition min. typ. max. unit reference section reference voltage 5.0 5.1 5.2 v i ref = 0 to 10ma; v cc = 8 to 55v * 4.950 5.1 5.250 v line regulation i ref = 0ma; v cc = 8 to 55v 510mv load regulation v ref = 0 to 5ma; v cc = 0 to 20ma 2 6 10 25 mv mv short circuit current 30 65 100 ma dc characteristics i qop total operating quiescent current 46ma i q quiescent current duty cycle = 0; v fb = 3.8v 2.5 3.5 ma error amplifier v fb voltage feedback input 3.33 3.36 3.39 v r l line regulation vcc = 8 to 55v 5 10 mv ref. voltage stability vs temperature * 0.4 mv/c v oh high level output voltage v fb = 2.5v 10.3 v v ol low level output voltage v fb = 3.8v 0.65 v i o source source output current v comp = 6v; v fb = 2.5v 180 220 m a i o sink sink output current v comp = 6v; v fb = 3.8v 200 300 m a i b source bias current 2 3 m a svrr e/a supply voltage ripple rejection v comp = v fb ; vcc = 8 to 55v 60 80 db dc open loop gain r l = 50 57 db gm transconductance i comp = -0.1 to 0.1ma v comp = 6v 2.5 ms oscillator section ramp valley 0.78 0.85 0.92 v ramp peak vcc = 8v 2 2.15 2.3 v vcc = 55v 9 9.6 10.2 v maximum duty cycle 95 97 % maximum frequency duty cycle = 0% r osc = 13k w , c osc = 820pf 300 khz electrical characteristics (continued) l4976 4/11
0 5 10 15 20 25 30 35 40 45 50 vcc(v) 1 2 3 4 5 iq (ma) 200khz r 1 =22k c 2 =1.2nf 0hz d97in724 tamb=25?c 0% dc 100khz r 1 =20k c 2 =2.7nf figure 1. quiescent drain current vs. input voltage. 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 i o (a) 3.360 3.362 3.364 3.366 3.368 3.370 3.372 3.374 3.376 3.378 v o (v) tj=25?c tj=125?c v cc =35v d97in734 figure 4. load regulation -50 -30 -10 10 30 50 70 90 110 tj(?c) 1 2 3 4 5 iq (ma) d97in731 0hz 200khz r 1 =22k c 2 =1.2nf v cc =35v 0% dc 100khz r 1 =20k c 2 =2.7nf figure 2. quiescent current vs. junction temperature 0 20 40 60 80 r1(k w ) 5 10 20 50 100 200 500 fsw (khz) d97in784 0.82nf 1.2nf 2.2nf 3.3nf 4.7nf 5.6nf tamb=25?c figure 5. switching frquency vs. r1 and c2 0 5 10 15 20 25 30 35 40 45 50 v cc (v) 3.370 3.371 3.372 3.373 3.374 3.375 3.376 3.377 v o (v) d97in733 tj=25?c tj=125?c figure 3. line regulation 0 5 10 15 20 25 30 35 40 45 50 v cc (v) 90.0 92.5 95.0 97.5 100.0 102.5 105.0 107.5 fsw (khz) d97in735 tj=25?c figure 6. switching frequency vs. input voltage. l4976 5/11
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 i o (a) 60 65 70 75 80 85 90 h (%) d97in739 v cc =8v fsw=100khz v o =3.36v v cc =12v v cc =24v v cc =48v figure 11. efficiency vs. output current. 0 5 10 15 20 25 v o (v) 82 84 86 88 90 92 94 96 h (%) d97in737 100khz v cc =35v i o =1.5a 200khz figure 9. efficiency vs output voltage. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 i o (a) 0.0 0.1 0.2 0.3 0.4 0.5 d v (v) tj=25?c tj=125?c d97in736 tj=-25?c figure 8. dropout voltage between pin 5 and 4. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 i o (a) 60 65 70 75 80 85 90 h (%) d97in738 v cc =8v fsw=100khz v o =5.1v v cc =12v v cc =24v v cc =48v figure 10. efficiency vs. output current. -50 0 50 100 tj(?c) 90 95 100 105 fsw (khz) d97in785 figure 7. switching frequency vs. junction temperature. 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 i o (a) 60 65 70 75 80 85 90 h (%) d97in740 v cc =8v fsw=200khz v o =5.1v v cc =12v v cc =24v v cc =48v figure 12. efficiency vs. output current. l4976 6/11
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 i o (a) 55 60 65 70 75 80 85 90 h (%) d97in741 v cc =8v fsw=200khz v o =3.36v v cc =12v v cc =24v v cc =48v figure 13. efficiency vs. output current. 0 1020304050v cc (v) 70 75 80 85 h (%) d97in742 v 0 =5.1v-f sw =100khz i o =1.5a v 0 =5.1v-f sw =200khz v 0 =3.36v-f sw =100khz v 0 =3.36v-f sw =200khz figure 14. efficiency vs. vcc. 0 1020304050v cc (v) 0 200 400 600 800 pdiss (mw) d97in743 i o =1.5a v o =5.1v fsw=100khz i o =1a i o =0.5a figure 15. power dissipation vs. vcc. 0 5 10 15 20 25 30 v 0 (v) 0 200 400 600 800 pdiss (mw) d97in744 i o =1.5a v cc =35v fsw=100khz i o =1a i o =0.5a figure 16. efficiency vs. vo. -50 -25 0 25 50 75 100 125 tj(?c) 2.3 2.4 2.5 2.6 2.7 2.8 2.9 ilim (a) d97in747 fsw=100khz v cc =35v figure 17. pulse by pulse limiting current vs. junction temperature. figure 18. load transient. l4976 7/11
10 10 3 10 5 10 7 f(hz) 10 2 10 4 10 6 10 8 -200 -150 -100 -50 gain (db) 0 50 phase 0 45 90 135 d97in787 gain phase figure 20. open loop frequency and phase of er- ror amplifier 2 1 d97in786 v cc (v) 30 20 10 v o (mv) 100 0 -100 1ms/div i o = 1a f sw = 100khz figure 19. line transient. l4976 8/11
outline and mechanical data dim. mm inch min. typ. max. min. typ. max. a 3.32 0.131 a1 0.51 0.020 b 1.15 1.65 0.045 0.065 b 0.356 0.55 0.014 0.022 b1 0.204 0.304 0.008 0.012 d 10.92 0.430 e 7.95 9.75 0.313 0.384 e2.54 0.100 e3 7.62 0.300 e4 7.62 0.300 f 6.6 0.260 i 5.08 0.200 l 3.18 3.81 0.125 0.150 z 1.52 0.060 minidip l4976 9/11
dim. mm inch min. typ. max. min. typ. max. a 2.35 2.65 0.093 0.104 a1 0.1 0.3 0.004 0.012 b 0.33 0.51 0.013 0.020 c 0.23 0.32 0.009 0.013 d 10.1 10.5 0.398 0.413 e 7.4 7.6 0.291 0.299 e 1.27 0.050 h 10 10.65 0.394 0.419 h 0.25 0.75 0.010 0.030 l 0.4 1.27 0.016 0.050 k 0? (min.)8? (max.) h x 45 a e b d e a1 h l c k 16 1 8 9 so16 wide outline and mechanical data l4976 10/11
information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsib ility for the cons equences 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 ? 2001 stmicroelectronics group of companies australia - brazil - china - finland - france - germany - hong kong - india - italy - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - u.s.a. http://www.st.com l4976 11/11

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