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june 2008 rev 4 1/30 30 l4988 low drop voltage regulator features operating dc supply voltage range 5.6v to 31v reset circuit sensing the output voltage down to 1v programmable reset pulse delay with external capacitor watchdog programmable watchdog timer with external capacitor enable input for en abling/disabling the watchdog functionality thermal shutdown and short circuit protection wide temperature range (t j = -40c to 150c) description the l4988 is a monolithic integrated 5v voltage regulator with a low drop voltage at currents up to 200ma. the output voltage regulating element consists in a p-channel mos and the regulation is performed regardless of input voltage transients up to 40v. the high precision of the output voltage is obtained with a pre-trimmed reference voltage. the l4988 is protected against short circuit and an over-temperature protection switches off the device in case of extremely high power dissipa- tion. the l4988 is active when the enable is high. state of the art features like reset and watchdog make this device particularly suitable to supply microprocessor system s in automotive applications. max dc supply voltage v s 40v max output voltage tolerance ? v 0 +/-2% max dropout voltage v dp 500 mv output current i 0 200 ma quiescent current i qn 75 a (1) 1. typical value wi th watchdog disabled. so-8 so-20 table 1. device summary package order codes tube tape & reel so8 L4988D L4988Dtr so20 (16+2+2) l4988md l4988mdtr www.st.com
contents l4988 2/30 contents 1 block diagram and pin co nfiguration . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.3 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4 electrical characteristics curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.5 test circuit and waveforms plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.5.1 load regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3 application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.1 voltage regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.2 reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3 watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4 package and pcb thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.1 so-8 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.2 so-20 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5 package and packing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.1 ecopack ? packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.2 so-8 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.3 so-20 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.4 so-8 packing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 5.5 so-20 packing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 6 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
l4988 list of tables 3/30 list of tables table 1. device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 table 2. pins description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 table 3. absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 table 4. thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 table 5. general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 table 6. reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 table 7. watchdog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 table 8. watchdog enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 table 9. so-8 thermal parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 table 10. so-20 thermal parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 table 11. so-8 mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 table 12. so-20 mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 table 13. document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
list of figures l4988 4/30 list of figures figure 1. block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 figure 2. pins configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 3. output voltage vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 4. output voltage vs. vs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 5. drop voltage vs. output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 6. current consumption vs. output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 7. current consumption vs. input voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 figure 8. current limitation vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 9. current limitation vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 10. short circuit current vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 11. short circuit current vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 12. v wen_high vs. tj. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 13. v wen_low vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 14. vrhth vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 15. vrlth vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 16. vwhth vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 17. vwlth vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 18. icr & icwc vs. tj. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 19. idr & icwd vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 20. twop vs. tj . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 21. psrr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 22. load regulation test circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 23. maximum load variation response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 24. l4988 application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 25. behavior of output current versus regulated voltage vo . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 26. reset timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 figure 27. watchdog timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 figure 28. so-8 pc board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 figure 29. so-8 rthj-amb vs. pcb copper area in open box free air condition . . . . . . . . . . . . . . . . . 18 figure 30. so-8 thermal impedance junction ambient single pulse . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 31. so-8 thermal fitting model of a single channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 32. so-20 pc board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 33. so-20 rthj-amb vs. pcb copper area in open box free air condition . . . . . . . . . . . . . . . . 21 figure 34. so-20 thermal impedance junction ambient single pulse . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 35. so-20 thermal fitting model of a single channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 36. so-8 package dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 figure 37. so-20 package dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 figure 38. so-8 tube shipment (no suffix) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 figure 39. so-8 tape and reel shipment (suffix ?tr?) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 7 figure 40. so-20 tube shipment (no suffix) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 figure 41. so-20 tape and reel shipment (suffix ?tr?) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
l4988 block diagram and pin configuration 5/30 1 block diagram and pin configuration figure 1. block diagram thermal protection watchdog reset voltage reference - + thermal protection thermal protection watchdog reset voltage reference voltage reference voltage reference - + v res v o v cr v s v cw v wen i o i s i cw 5v, 200 ma v wi gnd i wi i wen i cr i res
block diagram and pin configuration l4988 6/30 figure 2. pins configuration table 2. pins description pin name so8(d) s020(md) function wen 1 1 watchdog enable input if high watchdog functionality is active gnd 2 4 ground reference gnd 5, 6, 15, 16 ground. connected these pins to a heat spreader ground res 3 7 reset output. it is pulled down when output voltage goes below vo_th or frequency at wi is too low. vcr 4 10 reset timing adjust. a capacitor between vcr pin and gnd, sets the reset delay time (trd) vcw 5 11 watchdog timer adjust a capacitor between vcw pin and gnd, sets the time response of the watchdog monitor. wi 6 14 watchdog input. if the frequency at this input pin is too low, the reset output is activated. vo 7 17 voltage regulator output block to ground with a capacitor >100nf (needed for regulator stability) vs 8 20 supply voltage block to ground directly at ic pin with a capacitor n.c. 2, 3, 8, 9, 12, 13, 18, 19 not connected wen gnd res vcr 1 2 3 4 5 6 7 8 vs vo wi vcw wen n.c. n.c. gnd gnd gnd res n.c. n.c. vcr 10 9 8 7 6 5 4 3 2 1 20 n.c. n.c. vo gnd gnd wi n.c. n.c. vcw 11 12 13 14 15 16 17 18 19 vs so-8 so-20
l4988 electrical specifications 7/30 2 electrical specifications 2.1 absolute maximum ratings note: maximum ratings are absolute ratings; exceeding any one of these values may cause permanent damage to the integrated circuit. 2.2 thermal data table 3. absolute maximum ratings symbol parameter value unit v vsdc dc supply voltage -0.3 to 40 v i vsdc input current internally limited v vo dc output voltage -0.3 to 6 v i vo dc output current internally limited v wi watchdog input voltage -0.3 to v vo + 0.3 v v od open drain output voltage -0.3 to v vo + 0.3 v i od open drain output current internally limited v cr reset delay voltage -0.3 to v vo + 0.3 v v cw watchdog delay voltage -0.3 to v vo + 0.3 v v wen watchdog enable input voltage -0.3 to v vo +0.3 v t j junction temperature -40 to 150 ?c v esd esd voltage level (hbm-mil std 883c) 2 kv v esd esd voltage level (cdm aec-q100-011) 750 v table 4. thermal data symbol parameter s08 s016+2+2 unit r th-jamb thermal resistance junction to ambient 130 (1) 1. with copper area 2 cm 2 ; for details see figure 29 . 51 (2) 2. with copper area 6 cm 2 ; for details see figure 33 . c/w
electrical specifications l4988 8/30 2.3 electrical characteristics v s =5.6v to 31v, t j = -40c to +150c unless otherwise specified. table 5. general pin symbol parameter test condition min. typ. max. unit vo v o_ref output voltage vs = 6 to 31v io = 1 to 200ma 4.9 5.0 5.1 v vo i short short circuit current vs = 13.5v (1) 1. see figure 3 . 200 280 500 ma vo i lim (2) 2. measured output current when the output voltage has dropped 100mv from its nominal value obtained at vs=13.5v and io= 75ma . output current limitation vs = 13.5v (1) 200 350 600 ma vs, vo v line line regulation voltage vs = 6 to 31v io = 1 to 200ma 25 mv vo v load load regulation voltage io = 1 to 200ma 25 mv vs, vo v dp (3) 3. vs-vo measured when the output voltage has dr opped 100mv from its nominal value obtained at vs=13.5v and io= 75ma . drop voltage io = 200ma 270 500 mv vs, vo v dp (3) drop voltage io = 150ma 200 400 mv vs, vo svr ripple rejection fr = 100 hz (4) 4. guaranteed by design. 60 db vs, vo i qn_200 quiescent current vs=13.5v, io=200ma, wen = high 1.9 2.5 ma vs, vo i qn_50 quiescent current vs=13.5v, io= 50ma, wen = high 500 700 a vs, vo i q_1_we quiescent current vs=13.5v, io< 1ma, wen = high 93 200 a vs, vo i q_1_wd quiescent current vs=13.5v, io< 1ma, wen = low 75 150 a tw thermal protection temperature 150 190 c tw _ hy thermal protection temperature hysteresis 10 c
l4988 electrical specifications 9/30 table 6. reset pin symbol parameter test condition min. typ. max. unit res vres_l reset output low voltage r ext = 5k ? to vo, vo > 1v 0.4 v res i res_h reset output high leakage current v res = 5v 1 a res r_p_u pull up internal resistance with respect to vo 12 25 50 k ? res vo_th vo out of regulation threshold vs = 6 to 31v, io = 1 to 200ma 6% 8% 10% below v o_ref vcr vrlth reset timing low threshold vs = 13.5v 10% 13% 16% v o_ref vcr vrhth reset timing high threshold vs =13.5v 44% 47% 50% v o_ref vcr icr charge current vs = 13.5v 8 17.6 30 a vcr idr discharge current vs = 13.5v 8 17.6 30 a res trr_2 reset reaction time (1) 1. when vo becomes lower than 4v, t he reset reaction time decreases dow n to 2s assuring a faster reset condition in this particular case. vo = v o_ th -100mv 100 275 1000 s res trd reset delay time vs = 13.5v, ctr = 1nf 65 150 ms table 7. watchdog pin symbol parameter test condition min. typ. max. unit wi vih input high voltage vs = 13.5v 3.5 v wi vil input low voltage vs = 13.5v 1.5 v wi vih input hysteresis vs = 13.5v 500 mv wi ii pull down current vs = 13.5v 10 20 a vcw vwhth high threshold vs = 13.5v 44% 47% 50% v o_ref vcw vwlth low threshold vs = 13.5v 10% 13% 16% v o_ref vcw icwc charge current vs = 13.5v, vcw = 0.1v 4814a vcw icwd discharge current vs = 13.5v, vcw = 2.5v 1.0 2.1 4.5 a vcw twop watchdog period vs = 13.5v, ctw = 47nf 25 50 90 ms res twol watchdog output low time vs = 13.5v, ctw = 47nf 610.522ms
electrical specifications l4988 10/30 table 8. watchdog enable pin symbol parameter test condition min. typ. max. unit wen v en_l enable input low voltage 1 v wen v en_h enable input high voltage 3 v wen v en_hy enable input hysteresis 500 800 1100 mv wen i_leak pull down current wen = 5v 2 8 20 a
l4988 electrical specifications 11/30 2.4 electrical characteristics curves figure 3. output voltage vs. tj figure 4. output voltage vs. vs figure 5. drop voltage vs. output current figure 6. current consumption vs. output current figure 7. current consumption vs. input voltage figure 8. current limitation vs. tj -50 -25 0 25 50 75 100 125 150 tj(c ) 4,5 4,6 4,7 4,8 4,9 5 5,1 5,2 5,3 5,4 5,5 vo_ref (v) vs= 13.5v i0 = 75ma 0 5 10 15 20 25 30 35 vs (v ) 0 1 2 3 4 5 6 7 8 9 10 vo_ref (v) i 0 = 75 ma tj = 25 c 0 50 100 150 200 250 io (ma) 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 vdp (v) tj= 25 c tj= 125 c 0 40 80 120 160 200 240 io (ma) 0 300 600 900 1200 1500 1800 iqn (a) vs= 13.5 v tj= 25 c wen= high 0 5 10 15 20 25 30 35 vs (v ) 0 400 800 1200 1600 2000 2400 iqn(a ) tj = 25 c wen = high io = 1ma io = 50ma io= 100ma io= 200ma -50 -25 0 25 50 75 100 125 150 tj(c ) 0 100 200 300 400 500 600 ilim (ma) vs= 13.5v
electrical specifications l4988 12/30 figure 9. current limitation vs. input volt age figure 10. short circuit current vs. tj figure 11. short circuit current vs. input voltage figure 12. v wen_high vs. tj figure 13. v wen_low vs. tj figure 14. vrhth vs. tj 0 5 10 15 20 25 30 35 vs (v ) 250 275 300 325 350 375 400 ilim (ma) tj = 25 c tj = 125 c -50 -25 0 25 50 75 100 125 150 tj(c ) 0 100 200 300 400 500 600 ishort (ma) vs= 13.5v 0 5 10 15 20 25 30 35 vs (v ) 210 240 270 300 330 360 ishort (ma ) tj = 25 c tj = 150 c -50 -25 0 25 50 75 100 125 150 tj(c ) 1 1,5 2 2,5 3 3,5 4 vwen_high (v) vs= 5.6v to 31v -50 -25 0 25 50 75 100 125 150 tj(c ) 1,4 1,5 1,6 1,7 1,8 1,9 2 vwen_low (v) vs= 5.6v to 31v -50 -25 0 25 50 75 100 125 150 tj(c ) 30 35 40 45 50 55 60 vrhth (% vo_ref ) vs= 5.6v to 31v
l4988 electrical specifications 13/30 figure 15. vrlth vs. tj figure 16. vwhth vs. tj figure 17. vwlth vs. tj figure 18. icr & icwc vs. tj figure 19. idr & icwd vs. tj figure 20. twop vs. tj -50 -25 0 25 50 75 100 125 150 tj(c ) 0 10 20 30 40 50 vrlth (% vo_ref) vs= 5.6v to 31v -50 -25 0 25 50 75 100 125 150 tj(c ) 30 35 40 45 50 55 60 vwhth (% vo_ref ) vs= 5.6v to 31v -50 -25 0 25 50 75 100 125 150 tj(c ) 0 10 20 30 40 50 vwlth (% vo_ref) vs= 5.6v to 31v -50 -25 0 25 50 75 100 125 150 tj(c ) 0 5 10 15 20 25 30 icr & icwc (a) vs= 5.6v to 31v icr icwc -50 -25 0 25 50 75 100 125 150 tj(c ) 0 5 10 15 20 25 30 idr & icwd (a) vs= 5.6v to 31v idr icwd -50 -25 0 25 50 75 100 125 150 tj(c ) 20 30 40 50 60 70 80 twop (ms) vs= 5.6v to 31v ctw= 47nf
electrical specifications l4988 14/30 2.5 test circuit and waveforms plot 2.5.1 load regulation figure 22. load regulation test circuit figure 23. maximum load variation response figure 21. psrr 0 10 20 30 40 50 60 70 80 0,1 1 10 100 1000 10000 frequency [khz] psrr [db] c 0 = 4.7f 10 0,00e+00 5,00e-05 1,00e-04 1,50e-04 2,00e-04 2,50e-04 3,00e-04 3,50e-04 4,00e-04 time [s] v 0 [1v / div] i 0 [50ma / div]
l4988 application information 15/30 3 application information figure 24. l4988 application schematic note: the input capacitor cs > 200nf is necessary for the smoothing of line disturbances. the output capacitor c01 > 10 0nf is necessary for the stability of the regulation lo op. in order to damp output voltage oscillations during high load current surges, it is recommended to put an additional electrolytic capacitor c02 > 10f at the output pin. 3.1 voltage regulator voltage regulator uses a p-channel mos transistor as a regulating element. with this structure a very low dropout voltage at currents up to 200ma is obtained. the output voltage is regulated up to transient input supply voltage of 40v. no functional interruption due to over-voltage pulses is generated. a short circ uit protection to gnd is provided. the high precision of the output voltage is obtained with a pre-trimmed reference voltage. figure 25. behavior of output current versus regulated voltage vo thermal protection watchdog reset voltage reference - + thermal protection thermal protection watchdog reset voltage reference voltage reference voltage reference - + vi vs vcw cs ctw wi wen vcr ctr gnd res c 01 c 02 vo vo vo_ref iout ishort ilim
application information l4988 16/30 3.2 reset the reset circuit supervises the output voltage vo. the vo_th reset threshold is defined with the in-ternal reference voltage and a resistor output divider. if the output voltage becomes lower than vo_th then res goes low with a reaction time trr. the reset low signal is guaranteed for an output voltage vo greater than 1v. when the output voltage becomes higher than vo_th then res goes high with a delay trd. this delay is obtained by an internal oscillator. the oscillator period is given by: tosc = [(vrhth-vrlth) x ctr] / icr + [(vrhth-vrlth) x ctr] / idr where: icr: is an internally generated charge current idr: is an internally generated discharge current vrhth, vrlth: are two voltages defined with the output voltage and a resistor output divider ctr: is an external capacitance. trd is given by: trd = 512 x tosc reset is active when en is high. figure 26. reset timing diagram wi vo vcr res < trr trr tosc trd = 512 tosc vout_th vrhth vrlth
l4988 application information 17/30 3.3 watchdog a connected microcontroller is monitored by th e watchdog input wi. if pulses are missing, the reset output pin is set to low. the pulse sequence time can be set within a wide range with the external capacitor, ctw. the watchdog circuit discharges the capacitor ctw, with the constant current icwd. if the lower threshold vwlth is reached, a watchdog reset is generated. to prevent this the microcontroller must generate a positive edge during the discharge of the capacitor before the voltage has reached the threshold vwlth. in order to calculate the minimum time t, during which the micro-controller must output the positive edge, the following equation can be used: (vwhth-vwlth) x ctw = icwd x t every wi positive edge switches the current sour ce from discharging to charging. the same happens when the lower threshold is reached. when the voltage reaches the upper threshold, vwhth, the current switches from charging to discharging. the result is a saw-tooth voltage at the watchdog timer capacitor ctw. figure 27. watchdog timing diagram wi vcw res vwlth vwhth twop twol vwlth
package and pcb thermal data l4988 18/30 4 package and pcb thermal data 4.1 so-8 thermal data figure 28. so-8 pc board note: layout condition of r th and z th measurements (pcb fr4 area= 58mm x 58mm, pcb thickness = 2mm, cu thickness = 35m , copper areas: from minimum pad lay-out to 8cm 2 ) figure 29. so-8 r thj-amb vs. pcb copper area in open box free air condition 110 120 130 140 150 160 170 0 0,5 1 1,5 2 2,5 pcb cu heatsink area (cm^2) rthj_amb(c/w)
l4988 package and pcb thermal data 19/30 figure 30. so-8 thermal impedance junction ambient single pulse equation 1: pulse calculation formula where = t p /t figure 31. so-8 thermal fitting model of a single channel 1 10 100 1000 0,0001 0,001 0,01 0,1 1 10 100 1000 time (s) zth (c/w) footprint 2 cm 2 z th r th z thtp 1 ? () + ? =
package and pcb thermal data l4988 20/30 table 9. so-8 thermal parameter area/island (cm 2 )footprint2 r1 (c/w) 4.21 r2 (c/w) 2.11 r3 (c/w) 2 r4 (c/w) 41 r5 (c/w) 40 r6 (c/w) 58 40 c1 (w.s/c) 0.00029 c2 (w.s/c) 0.0024 c3 (w.s/c) 0.03 c4 (w.s/c) 0.04 c5 (w.s/c) 0.1 c6 (w.s/c) 1.05 2
l4988 package and pcb thermal data 21/30 4.2 so-20 thermal data figure 32. so-20 pc board note: layout condition of r th and z th measurements (pcb fr4 area= 58mm x 58mm,pcb thickness = 2mm, cu thickness=35 m , copper areas: from minimum pad lay-out to 8cm 2 ). figure 33. so-20 r thj-amb vs. pcb copper area in open box free air condition 50 52 54 56 58 60 62 64 66 68 70 01234567 pcb cu heatsink area (cm^2) rthj_amb(c/w)
package and pcb thermal data l4988 22/30 figure 34. so-20 thermal impedance junction ambient single pulse equation 2: pulse calculation formula where = t p /t figure 35. so-20 thermal fitting model of a single channel 1 10 100 0,0001 0,001 0,01 0,1 1 10 100 1000 time (s) zth (c/w) footprint 2 c m 2 z th r th z thtp 1 ? () + ? =
l4988 package and pcb thermal data 23/30 table 10. so-20 thermal parameter area/island (cm 2 )footprint2 r1 (c/w) 4.21 r2 (c/w) 2.11 r3 (c/w) 2.2 r4 (c/w) 10 r5 (c/w) 15 r6 (c/w) 35 18 c1 (w.s/c) 0.00029 c2 (w.s/c) 0.0024 c3 (w.s/c) 0.015 c4 (w.s/c) 0.15 c5 (w.s/c) 1.5 c6 (w.s/c) 4 7
package and packing information l4988 24/30 5 package and packing information 5.1 ecopack ? packages in order to meet environmental requirements, st offers these devices in ecopack ? packages. these packages have a lead-free second-level interconnect. the category of second-level interconnect is marked on the package and on the inner box label, in compliance with jedec standard jesd97. the maximum ratings related to soldering conditions are also marked on the inner box label. ecopack is an st trademark. ecopack specifications are available at: www.st.com. 5.2 so-8 package information figure 36. so-8 package dimensions
l4988 package and packing information 25/30 table 11. so-8 mechanical data symbol millimeters min. typ. max. a 1.75 a1 0.10 0.25 a2 1.25 b 0.28 0.48 c 0.17 0.23 d (1) 4.80 4.90 5.00 e 5.80 6.00 6.20 e1 (2) 3.80 3.90 4.00 e1.27 h 0.25 0.50 l 0.40 1.27 l1 1.04 k0 8 ccc 0.10 1. dimensions d does not include mold flash, protrusions or gate burrs. mold flash, potrusions or gate burrs shall not exceed 0.15mm in total (both side). 2. dimension ?e1? does not include interlead flash or pr otrusions. interlead flash or protrusions shall not exceed 0.25mm per side.
package and packing information l4988 26/30 5.3 so-20 package information figure 37. so-20 package dimensions table 12. so-20 mechanical data symbol millimeters min. typ. max. a 2.35 2.65 a1 0.10 0.30 b 0.33 0.51 c 0.23 0.32 d (1) 1. ?d? dimension does not include mold flash, protusions or gat e burrs. mold flash, protusions or gate burrs shall not exceed 0.15mm per side. 12.60 13.00 e 7.40 7.60 e1.27 h 10.0 10.65 h 0.25 0.75 l 0.40 1.27 k0 8 ddd 0.10
l4988 package and packing information 27/30 5.4 so-8 packing information figure 38. so-8 tube shipment (no suffix) figure 39. so-8 tape and reel shipment (suffix ?tr?) all dimensions are in mm. base q.ty 100 bulk q.ty 2000 tube length ( 0.5) 532 a 3.2 b 6 c ( 0.1) 0.6 c b a tape dimensions according to electronic industries association (eia) standard 481 rev. a, feb. 1986 all dimensions are in mm. tape width w 12 tape hole spacing p0 ( 0.1) 4 component spacing p 8 hole diameter d (+0.1/-0) 1.5 hole diameter d1 (min) 1.5 hole position f ( 0.05) 5.5 compartment depth k (max) 4.5 hole spacing p1 ( 0.1) 2 top cover tape end start no components no components components 500mm min 500mm min empty components pockets saled with cover tape. user direction of feed reel dimensions all dimensions are in mm. base q.ty 2500 bulk q.ty 2500 a (max) 330 b (min) 1.5 c ( 0.2) 13 f 20.2 g (+ 2 / -0) 12.4 n (min) 60 t (max) 18.4
package and packing information l4988 28/30 5.5 so-20 packing information figure 40. so-20 tube shipment (no suffix) figure 41. so-20 tape and reel shipment (suffix ?tr?) base q.ty 40 bulk q.ty 800 tube length ( 0.5) 532 a 3.5 b 13.8 c ( 0.1) 0.6 a c b base q.ty 1000 bulk q.ty 1000 a (max) 330 b (min) 1.5 c ( 0.2) 13 d 20.2 g (+ 2 / -0) 24.4 n (min) 60 t (max) 30.4 tape dimensions according to electronic industries association (eia) standard 481 rev. a, feb. 1986 all dimensions are in mm. tape width w 24 tape hole spacing p0 ( 0.1) 4 component spacing p 12 hole diameter d (+0.1/-0) 1.5 hole diameter d1 (min) 1.5 hole position f ( 0.05) 11.5 compartment depth k (max) 6.5 hole spacing p1 ( 0.1) 2 top cover tape end start no components no components components 500mm min 500mm min empty components pockets saled with cover tape. user direction of feed reel dimensions
l4988 revision history 29/30 6 revision history table 13. document revision history date revision changes 01-jun-2007 1 initial release 30-aug-2007 2 added features table. added list of tables and figures. updated section 2.3: electrical characteristics . added section 4: package and pcb thermal data . added so-8 packing information and so-20 packing information . 13-feb-2008 3 update section 2.3: electrical characteristics . 04-jun-2008 4 document restructured. changed figure 1: block diagram . updated features table on cover page: changed quiescent current value from 80 to 75 a. updated table 5: general : ? changed i short typical value from 250 to 280 ma ? changed i qn_50 typical value from 550 to 500 a ? changed i q_1_we typical value from 130 to 93 a ? changed i q_1_wd typical value from 80 to 75 a. updated table 7: watchdog : ? changed vwlth values in v o_ref percentages ? changed vwhth values in v o_ref percentages. added figure 24: l4988 application schematic . added section 2.4: electrical characteristics curves . added section 2.5: test circuit and waveforms plot .
l4988 30/30 please read carefully: information in this document is provided solely in connection with st products. stmicroelectronics nv and its subsidiaries (?st ?) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described he rein at any time, without notice. all st products are sold pursuant to st?s terms and conditions of sale. purchasers are solely responsible for the choice, selection and use of the st products and services described herein, and st as sumes no liability whatsoever relating to the choice, selection or use of the st products and services described herein. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. i f any part of this document refers to any third party products or services it shall not be deemed a license grant by st for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoev er of such third party products or services or any intellectual property contained therein. unless otherwise set forth in st?s terms and conditions of sale st disclaims any express or implied warranty with respect to the use and/or sale of st products including without limitation implied warranties of merchantability, fitness for a parti cular purpose (and their equivalents under the laws of any jurisdiction), or infringement of any patent, copyright or other intellectual property right. unless expressly approved in writing by an authorized st representative, st products are not recommended, authorized or warranted for use in milita ry, air craft, space, life saving, or life sustaining applications, nor in products or systems where failure or malfunction may result in personal injury, death, or severe property or environmental damage. st products which are not specified as "automotive grade" may only be used in automotive applications at user?s own risk. resale of st products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by st for the st product or service described herein and shall not create or extend in any manner whatsoev er, any liability of st. st and the st logo are trademarks or registered trademarks of st in various countries. information in this document supersedes and replaces all information previously supplied. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners. ? 2008 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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