LM2596 1 LM2596 3a s tep-down v o lt age regulator genaral descripti on t he LM2596 s e ries of regul at ors are monol ithi c integrated circuits that pr ovide all th e ac tive functio ns for a step-d o w n (buck) s w itchi n g regul ator, ca pabl e of drivin g a 3a loa d w i th exc ell ent li ne an d loa d regul atio n. t h e s e devices ar e available in fixed output voltages of 3.3v , 5v, 12v, and an adjustable out put version. requ irin g a minimum num b e r of external compone nts, t hese regulat ors are simple to use and include inter n al frequenc y c o m pens ation?, and a fixed-frequenc y oscil lator. t he LM2596 series operates at a s w itchin g frequenc y of 150 khz thus allo w i ng smaller sized filter components than w h at w o ul d be nee ded w ith lo w e r frequenc y s w itc hin g regul at ors. availabl e in a standar d 5-lead t o -220 package w it h several different lead bend options, and a 5-lead t o -263 surface mount package. a standard ser ies of inductor s are available from several different manufact urers optimized for use w i t h the LM2596 series. t h is feature greatly simplifies the design of s w itch- mode po w e r s uppl ies. other features include a guaranteed 4 % t o lerance on output voltage under specified input voltage a nd output load conditi ons, and 15% on the osci llator fre quenc y . e x t e rnal sh utdo w n is incl ude d, feat uring t y pica ll y 80 a stand b y current. self protection featur es inclu de a t w o stage frequenc y reduci ng c u rrent lim it for the output s w itc h and an over temperatur e shutdo w n for complete pr otection under fault conditions. ordering informa tion output voltage 3.3 5.0 12 adj package type LM2596s-3.3 LM2596s-5.0 LM2596s-12 LM2596s-adj to-263 LM2596t-3.3 LM2596t-5.0 LM2596t-12 LM2596t-adj to-220 pin connection fea tures ? 3.3v, 5v, 12v, and adjustable output versions ? adjustable v e r sion output voltage range, 1.2v to 37v 4 % ma x over lin e an d lo ad con ditio ns ? availa bl e in t o -220 a nd t o -2 63 pack ages ? guaranteed 3a output load current ? input voltage range up to 40v ? requires only 4 ext ernal com ponents ? excellent line and load regulat ion specificati ons ? 150 khz fi xe d frequ enc y inter nal osci llat or ? tt l shutdo w n capa bilit y ? lo w po w e r standby mode, iq typically 80 a ? high effici enc y ? uses readily available standard inductors ? th e rm a l s h utdo wn a n dcu rr e n t limi tp r otect i o n applica ti ons ? simple high-efficienc y step -dow n (buck) regulator ? on-card s w itching regul ators ? positive to n egative conv erter bent and staggered leads, through hole package 5-lead to-220 (t) surface mount package 5-lead to-263 (s) order number LM2596t-3.3, LM2596t-5.0, LM2596t-12 or LM2596t-adj order number LM2596s-3.3, LM2596s-5.0, LM2596s-12 or LM2596s-adj http://
LM2596 2 typical applica tion (fixed output v o lt age v e rs ions) block diagram
LM2596 3 abs olute maxi mu m ra tin gs (note 1) m a x i m u m s u p p l y v o l t a g e 4 5 v on /off pin input voltage -0.3 d v d +25v feedb ack pin voltag e -0.3 d v d +25v output voltage to ground (steady state) -1v p o w e r d i s s i p a t i o n i n t e r n a l l y l i m i t e d storage t e mperature r ange -65c to +150c esd suscepti b ilit y human b o d y model (n ote 2) 2 kv lea d t e mperature s package vapor phase ( 60 sec.) +215c infrared (10 sec.) +245c t package (solderi ng, 10 sec. ) +260c maximum junc tion t e mperatu re +150c ope rating rati ngs t e mperature r ang e -40c ? t j ? +125c s u p p l y v o l t a g e 4 . 5 v t o 4 0 v LM2596-3.3 electri cal characteristi cs specification s w i th standard t y pe f a ce are for t j = 2 5 c, and th ose with bold face t y p e appl y over full operating temp erature range. LM2596-3.3 symbol parameter conditions ty p e (note 3) limit (note 4) units (limits) system parameters (note 5) test circuit figure 1 v out output voltage 4.75v ? v in ? 40v, 0.2a ? i loa d ? 3a 3.3 3.168/ 3.1 35 3.432/ 3.465 v v(min) v(max) efficiency v in = 12v, i lo ad = 3a 73 % LM2596-5.0 electri cal characteristi cs specification s w i th standard t y pe f a ce are for t j = 2 5 c, and th ose with bold face t y p e appl y over full operating temp erature range. LM2596-5.0 symbol parameter conditions ty p e (note 3) limit (note 4) units (limits) system parameters (note 5) test circuit figure 1 v out output voltage 7v ? v in ? 40v, 0.2a ? i load ? 3a circuit of f i gur e 2 5.0 4.800/ 4.7 50 5.200/ 5.250 v v(min) v(max ) efficiency v in = 12v, i lo ad = 3a 80 % LM2596-12 electri cal characteristi cs specification s w i th standard t y pe f a ce are for t j = 2 5 c, and th ose with bold face t y p e appl y over full operating temp erature range. LM2596-12 symbol parameter conditions ty p e (note 3) limit (note 4) unit s (limit s) system parameters (note 5) test circuit figure 1 v out output voltage 15v ? v in ? 40v, 0.2a ? i load ? 3a 12 11.52/ 1 1 .40 12.48/ 12 .6 0 v v(min) v(max ) efficiency v in = 25v, i lo ad = 3a 90 % LM2596-adj electri cal characteri sti cs specification s w i th standard t y pe f a ce are for t j = 2 5 c, and th ose with bold face t y p e appl y over full operating temp erature range. LM2596-adj symbol parameter conditions ty p e (note 3) limit (note 4) units (limits) system parameters (note 5) test circuit figure 1 v fb feedb ack volt age 4.5v ? v in ? 40v, 0.2a ? i load ? 3a v out programmed for 3v, circuit o f figure 1 1.230 1.193/ 1.1 80 1.267/ 1.280 v v(min) v(max) efficiency v in = 12v, v ou t = 5 v , i load = 3a 73 %
LM2596 4 all out p ut volt age ve rsi ons ele ct rical characte ris tics specification s w i th standard t y pe face are for t j = 25c, and those w i th b o ld face t y pe appl y ov er f u ll operati ng te m p eratur e range. unless otherw ise specified, v in = 12v for the 3. 3v, 5v, and adjustable version, v in = 24v for the 1 2 v version. i lo ad = 5 00 ma. LM2596-xx symbol parameter conditions ty p e (note 3) limit (note 4) unit s (limit s) device parameters i b feedback bias current adjustable version only, v fb = 1.3v 10 50/ 10 0 na na (max ) f o oscillator freq uenc y (note 6) 150 127/ 1 10 173/ 17 3 khz khz(min) khz(max ) v sat saturation volt age i out = 3a (note 7,8) 1.16 1.4/ 1.5 v v(max ) dc ma x du ty cy cle (on ) min dut y cy cle (off) (note 8) (note 9) 100 0 % i cl current lim it peak current (notes 7, 8) 4.5 3.6/ 3.4 6.9/ 7.5 a a(min) a(max ) output = 0v (notes 7, 9) 50 a(max) i l output leak age current output = -1v (notes 10) 2 30 ma ma(max ) i q quiescent curr ent (note 9) 5 10 ma ma(max ) i st b y standby qui es cent current on /off pin = 5v (off) (notes 10) 80 200/ 25 0 a a(max ) jc ja ja ja ja t hermal resistance to-220 or t o -263 pack age, junction to case to-220 package, junction to ambient (not e 11) to-263 package, junction to ambient (not e 12) to-263 package, junction to ambient (not e 13) to-263 package, junction to ambient (not e 13) 2 50 50 30 20 c/w on /off control test circuit figure 1 v ih v il on /off pin logic input t h reshold volt age lo w (regul ator on) high (regulator off) 1.3 0.6 2.0 v v(max ) v(min) i ih v logic =2.5v (regulator off) 5 15 a a(max ) i il on /off pin input current v logic =0.5v ( r egulator on) 0.02 5 a a(max ) note 1: absolute max i mum rati ngs indi cate limits be y o nd which damag e to the de v ice ma y occ ur. o perating ra tings indi cate conditi ons for which the de v i c e is intende d to b e func ti onal, bu t do n o t gu ar antee s pecific perfor mance li mits. fo r gu arantee d speci ficatio ns and t e st co nditio n s , see th e elec trical characte ristics. note 2: t he human bod y mo del is a 100 pf capa citor di schar ged thro ugh a 1.5k r e sistor in to eac h pin. note 3: t y pical num bers are at 25 c an d represe nt the most li kel y norm . note 4: all limits g uarante ed at r oom t e mperat ure (sta ndar d t y pe fa ce) an d at temperat ure e xtrem es (bold t ype fa ce). all room t e mper atu re limits ar e 100 % producti on te sted. all limits at te mpera tur e e x tre mes are g u ar anteed v ia correla tio n using sta ndard sta tistical qualit y con tr ol (sqc ) met hods. a ll limits are used to calculate a v er age o u tgoing qualit y le v e l (aoql). note 5: e x tern al co mponent s suc h as t h e catch diode, induc t o r, input and output c apacitors , and voltag e progra mming resist ors can affec t s w itchi ng regul ator sy s tem p e rform ance. w hen the LM2596 i s used a s sho wn in t he figur e 1 te st circu it, s y stem perfo rman ce w ill be as sh o w n i n s y stem para meters section of electrical chara cteris tics. note 6: t he sw i tchin g freque nc y is r educ ed w hen the s e cond stage cu rrent li mit is acti v a te d. note 7: no dio de, in ductor or capa citor c onnecte d to o u tput pi n. note 8: feedb ack pi n remo v e d from outp ut and c onnec ted t o 0v to for ce th e outp u t transist or s w itc h o n. note 9: feedba ck pi n remo v e d from o u tp ut and co nnect ed to 12v for th e 3.3v , 5v, and the a dj. v e r sio n, and 15 v for th e 12 v version, to f orc e th e output t r ansist or sw i tch o ff. note 10: v in = 40 v. note 11: juncti on to ambient therm al resi stance ( no e x t e rnal h eat sink) for th e t o-220 pac kage mount e d verticall y, w ith the l eads sol der ed to a p r inted circ uit bo ar d w it h (1 o z.) cop per ar ea of ap pro x im atel y 1 in 2 . note 12: juncti on to ambient therm al resi stance w i th th e t o-263 pack age ta b sold ered to a singl e print ed circuit board w ith 0.5 in 2 of (1 oz .) cop per area . note 13: juncti on to ambient therm al resi stance w i th th e t o-263 pack age ta b sold ered to a singl e side d printed circuit boar d w ith 2. 5 in 2 o f (1 oz .) copper area. note 14: juncti on to ambient therm al resi stance w i th th e t o-263 pack age ta b sold ered to a dou ble sid e d printed circuit boar d w ith 3 i n2 of (1 oz.) copper area o n the l m 2 596s side o f the boa rd, an d app r o x i matel y 16 in 2 of c opper o n the other s i de of th e p-c board.
LM2596 5 typical performance characteri sti cs (circuit of figure 1 ) normalized output voltage line regulation efficiency switch saturation voltage switch current limit dropout voltage operating quiescent current shutdown quiescent current minimum operating supply voltage on /off threshold voltage on /off pin current (sinking) switching frequency
LM2596 6 typical performance characteri sti c s (circuit of figure 1 ) (continued) feedback pin bias current continuous mode switching waveforms v in = 20v, v out = 5v, i load =2 a l = 32 h, c out = 220 f, c out e s r=5 0 m ? discontinuous mode switching waveforms v in = 20v, v out = 5v, i load = 500 ma l = 10 h, c out = 330 f, c out e s r=4 5 m ? horizontal time base: 2 s/div. a: output pin voltage, 10v/div. b: inductor current 1a/div. c: output ripple voltage, 50 mv/div. horizontal time base: 2 s/div. a: output pin voltage, 10v/div. b: inductor current 0.5a/div. c: output ripple voltage, 100 mv/div. load transient response for continuous mode v in = 20v, v out = 5v, i load = 500 ma to 2a l = 32 h, c out = 220 f, c out esr=5 0 m ? load transient response for discontinuous mode v in = 20v, v out = 5v, i load = 500 ma to 2a l = 10 h, c out = 330 f, c out esr=4 5 m ? horizontal time base: 100 s/div. a: output voltage, 100 mv/div. (ac) b: 500 ma to 2a load pulse horizontal time base: 200 s/div. a: output voltage, 100 mv/div. (ac) b: 500 ma to 2a load pulse
LM2596 7 test circuit and l a yout gui delines as in any s w it ching regul ator , lay out is ver y importan t. rapidl y s w itching currents associated w i th w i ri ng inductanc e can gener ate voltage transi ents w h ic h can cause pro blems. for minim al inductance and ground loops, the w i res indic ated b y hea v y lines should be w i de pr inted circuit tr aces and should be kept as short as pos sible. for bes t results, ext ernal components shoul d be l o cated as cl o s e to the s w i t cher lc as p o ssibl e usi ng grou nd pl ane construction or single poi nt grounding. if open core inductors are used, special care must be taken as to the loc ati on and positioning of this t y pe of inductor. allo w i ng the inductor flux to intersect sensitiv e feedback, lc groundpath and c out w i ring can caus e probl ems. when using the adjustable version, special care must be taken as to the location of the feedback resistors and the associated wiring. physically locate both resistors near the ic, and route the wiring away from the inductor, especially an open core t y pe of inducto r . fixed output voltage versions c in ? 470 f, 50v, aluminum electrolytic nichicon ?pl series? c out ? 220 f, 25v aluminum electrolytic, nichicon ?pl series? d1 ? 5a, 40v schottky rectifier, 1n5825 l1 ? 68 h, l38 adjustable output voltage versions where v ref = 1.23v select r 1 to be approximately 1 k ? , use a 1% resistor for best stability . c in ? 470 f , 50v , aluminum electrolytic nichicon ?pl series? c out ? 220 f , 35v aluminum electrolytic, nichicon ?pl series? d1 ? 5a, 40v schottky rectifier , 1n5825 l1 ? 68 h, l38 r1 ? 1 k ? ,1 % c ff ? see application information section figure 1. standard test circuits and layout guides
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