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lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch general description the lsp650 1 is a curr ent mode step up conv erter th at ca n car r y out 1.6 a . l sp6501 also builds up a intern al s w i t c h w i th 0.23 ? to prov ide a high efficie n t regula t or w i th fas t r espon se. th e lsp6501 ca n be operated at 640 khz or 1.3m hz allo w i ng for small filter solution and lo w noise. an exte r nal co mpensa tion pin giv e s the use r flexibilit y in setting up loop compensation, w h ich allo w s to use a lo w - esr cer amic outpu t capaci tors. intern al soft-star t fun c tio n results in small inrush curren t a nd the so fe -start c a n b e programmed w i th an external capacitor. the lsp650 1 dev i ce in cludes und e r -v oltage lockout, and current limiting protec tio n prev enting damage in the e v ent of an outpu t o v erload. a l o w profile 8-pin msop packages is av ailable in the lsp6501. features 1. 1.6a, 0.23 $ , internal sw itch 2. input range: +2.6v to +5.5v 3. low shut dow n current: 0.1ua 4. adjust able frequency : 640khz or 1.3mhz 5. small 8-pin msop package typical applications tft -lcd pow e r management port able dvd play er pow e r management pin assignment ver. 1.2 1/10 1 2 3 4 8 7 6 5 fb v dd freq ss sw shdn com p msop-8 (t op v i ew ) gn d pin description p i n n a m e f u n c t i o n 1 comp compensation pin for error amplifier 2 f b feedb ack pin with a typica l referen c e v o ltage of 1.24 v, v out = 1.24 ? (1 + r1/r 2 ) . 3 shdn shutdown control pin. when s hdn is low, the lsp6501 will turn off 4 g n d g r o u n d 5 s w switc h p i n 6 v dd power supply pin 7 f r e q frequency select pin. oscillator frequ ency to 640khz when f r eq is low, and 1.3mhz when freq is high 8 ss soft-start control pin.
lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch t y p i c a l a p p l i c a t i o n c i r c u i t b s o l u t e m a x i m u m r a t i n g s a 304 vc c ss gnd fb d f l sw fr eq com p r p c p2 2 . 6 ~ 5.5 v dc c out c in c p1 r 1 r 2 v in v out c ss c 3 r 3 lsp6501 a v a lue unit parameters ver. 1.2 2/10 sw to gnd 18 v input v o lt a g e : s h d n / v dd / freq to gnd 6 v ss to gnd -0.3 ~ + 0.3 v d d v s w p i n m a x i m u m c u r r e n t 2 . 3 a operating temperature -20 ~ +85 c m a x i m u m o p e r a t i n g j u n c t i o n t e mperature, t j 150 c s t orage t e m peratu r e ran g e -45 to 125 c lead t e m p e r a t u r e ( s o l d e r i n g , 1 0 s e c o n d s ) 260 c n o t e : e x c e e d i ng these rati ngs coul d ca u s e d current s are positive into, negative o a ma ge to t he device. all volt re spe c t to gro und. u t o f t h e s p e c i f i e d t e r m i n a l . a r e with g e s a h e r m a l i m p e d i e n c e t thermal resist a n c e f r o m j u n c t i o n t o ambient, ja 152 c /w l e c t r i c a l c h a r a c t e r i s t i c s e dd a min t y p max u nit (v = shdn ____ ___ ___ =3v, freq=gnd; t =25c, unless otherwise noted) parameter symbol conditions i n p u n g e t v o lt a g e r a v dd 2 . 6 5 . 5 v v dd uvlo when v dd is rising, typical hysteresis ; sw remains of 2.25 2.38 2.52 under vol t age lo ckout is 40mv f below this level v quiescent current i dd fb v fb =1. 0 v , swit ching 1.2 5.0 ma ma v = 1 .3v , n o t s w itc h ing 0.21 0.35
lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch ver. 1.2 3/10 shut down current i sc shdn ____ ___ ___ = gnd 0 . 1 1 0 ua fb reference v o lt age v fb 1 . 2 2 8 1.252 1 . 2 4 v fb input current i bias v fb =v ref 1 4 0 na fb v o lt age line regulation comp=fb, 2.6v ? v dd ? 5.5v - 0.1 0.15 %/v error amp a n s c o n d u c t a n c e t r * gm 7 i com p = ? 5 u a 0 1 0 5 2 4 0 ua/ v e r r n * o r a m p g a i a v - 1500 - v/v freq=gnd 540 640 740 oscillated frequency fosc freq=v 1 100 1 6 dd 1 3 2 0 0 0 khz f r e q = g n d 7 9 8 5 9 2 maximum duty cycle d ma x freq=v dd 8 5 % current limit i lim v dd =1v , d = 0 . 6 5 1.2 1.6 2.3 a on-resist ance r on 0.23 0.5
i s w = 1 . 2 a leakage current i sw off v = 1 2 v sw 0 . 0 1 2 0 ua r e s n c e e t s w i t c h r e s i s t a 300
sof n t 1.5 t s t a r t c h a r g e c u r r e iss vss=1.2v 4 7 ua input low v o lt age v shdn ____ ___ ___ , freq; v . 0 il dd = 2 .6v to 5.5v . 3 v dd v input high v o lt age v ih shdn ____ ___ ___ , freq; v dd . 0 dd = 2 .6v to 5.5v . 7 v v h y s t e r e s i s shdn ____ ___ ___ , freq; 0 . 1 dd v v freq pull-down current i 5.0 9.0 freq 1 . 8 ua shdn input current i shut n dow 0 . 0 0 1 1 ua *: guaranteed by design, not 100% tested in production. functional block diagram 1 dri v er fb ram p s u mme r pw m com p arat or error a mp 63 m ? sy nc s logi c control r sw it ch os c i l l at or e ? ? e 1. 24 v ref e renc e 2 7 3 6 4 8 5 gnd shdn v dd sw ss com p freq curr ent sens e sl op e com pens at ion
lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch t y p i c a l c h a r a c t e r i s t i c s unless otherwise specified, t a = 25c. e f f i ci e n c y vs . o u t p u t c u r r e n t 40 % 50 % 60 % 70 % 80 % 90 % 10 0% 0 4 0 8 0 120 16 0 2 0 0 o u tp u t c u r r e n t ( m a ) e ffi ci e n cy fo s e = 1 . 2 m h z l= 4 . 7 u h v in =2 . 7 v v in =3 . 3 v v in =5 v e f f i ci e n cy vs . o u t p u t c u r r e n t 10 0% 40 % 50 % 60 % 70 % 80 % 90 % 0 4 0 8 0 120 16 0 2 0 0 o u t p u t cu r r e n t ( m a ) e f f i ci e n cy f o se = 6 40 k h z l= 4 . 7 u h v in =2 . 7 v v in =3 . 3 v v in =5 v ver. 1.2 4/10 o u tput v o l t a g e v s . loa d c u r r e nt 7. 0 8. 0 9. 0 10. 0 0 4 0 8 0 120 160 200 load c u r r e n t ( m a ) ou t put vol t age (v) fos c = 6 4 0 k h z vin = 3 . 3 v o u t put v o l t a g e v s . loa d c u r r e nt 7. 0 8. 0 9. 0 10. 0 0 4 0 8 0 120 160 200 load c u r r e n t ( m a ) o u t p u t vo lt ag e ( v ) fos c = 1 . 2 m h z vin = 3 . 3 v c u r r e nt li m i t v s . d u t y c y c l e 1. 4 1. 6 1. 8 2. 0 2. 2 2. 4 20% 40% 60% 80% d u ty ( % ) li m i t c u rr en t ( a ) l= 4 . 7 u h 64 0k h z 1. 2 m h z m a x loa d c u r r e nt v s . i n p u t v o l t a g e 350 460 570 680 790 900 2. 5 3 . 0 3. 5 4 . 0 4. 5 5 . 0 i nput vol t age ( v ) o u tp u t c u r r e n t ( m a ) vin = 3 . 3 v l= 4 . 7 u h 640 k h z 1. 2 m h z
lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch f u n c t i o n d e s c r i p t i o n package a 304 vc c ss fb gnd d f l sw fr eq com p r p c p2 2 . 6 ~ 5.5 v dc c out c in c p1 r 1 r 2 v out c ss c 3 r 3 lsp6501 v in c.r no q?ty value description ic 1 - lsp6501 msop-8 d - schottky diode 40v/2a sma f 1 c 10uf / 10v c a p c s m ver. 1.2 5/10 in 1 e r s m d d 1 2 0 6 c o u t u f / 2 5 v s m d 2 1 0 c a p c e r s m d 1 2 0 6 l 1 4 . 7 u h 1.0a n r 4 0 1 8 - 1 0 0 m s m d r 1 1 * not e 1 c h i p r e s i s t o r / 1 % smd 0603 r 2 1 12k c h i p r e s i s t o r / 1 % smd 0603 r p 1 10k chip resistor / 1% s m d 0 6 0 3 (r 3 ) * not e 2 o n a l ) 1 ( o p t i chip resistor / 1% smd 0603 (c 3 ) * not e 2 n a l ) 1 ( o p t i o cap cer x7r smd 0603 (c p 1 ) n a l ) 1 ( o p t i o cap cer x7r smd 0603 c p 2 1 10nf cap cer x7r smd 0603 c s s 1 1uf cap cer x7r smd 0603 *no t e fb (1+r 1 /r 2 ) *note 2: r 3 & c 3 & c p1 d prov in g t h ance. b eca o n e n t s are not ideal, s o m e e s the syste m n e e d s r g e t be tt e r e v a l u e is c o r d i n g t o r e a l l o a d c o n d i t i o n s . 1. s e t t i n g t h e o f b p i n l sp6501. by usin g the resi stor divider, r 1 and r 2 , t o f e e d b a c k s i g n a l , the output voltage is determined by: 1 : v o u t =v are use for i m e tr ansie n t p e r f o r m u s e th e c o m p ti m 3 & c 3 & c p1 t o t r a n s i ent . t h determ i n e d a c u t p u t v o l t a g e i s u s e d t o s e t the output voltage v out of t h e divide v out t o t h e f b p i n a s 2 1 2 r r r v v out fb + ? = ? ? ? ? ? ? ? ? + ? = ? ? ? ? ? ? ? ? + ? = 2 1 2 1 1 24 . 1 1 r r v r r v v fb out where, the feedback pin voltage, v fb , is fixed at 1.24v. 2. selection of output capacitor the capa citan c e is high eno ug h and the esr (effective s e (high cap a ci tan c e & lo w esr) a r e very importa nt for the boo s t v out ripple and load transient specifications. it is recomme nded to sele ct output capa citors that serie s re si stance) i s low enou gh. the c o n v e r t e r t o b e a b l e t o m e e t t h e cerami c cap a citors often have low esr and can m eet the boost converte r re quire ment s as long as the cap a cita nce value s are en o ugh. note tha t the capacita n ce value s of all kinds of cerami c ca pa citor drop whe n
lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch ver. 1.2 6/10 there are dc voltages bia s on them. the highe r the dc bias, the l o w e r t h e e f f e c t i v e c a p a ci tance. the z xx seri e i t o r s a r e s i m i l a r . s cap a ci tors (ex: z5u) often dro p more cap a cit anc e than wh at yxx serie s cap a cito rs (e x: y5v) will drop. and yxx seri es a r e usuall y worse th an xxx serie s (ex: x5r). t h erefo r e, it is better to u s e x5r/x7r typ e of cerami c capa citors and do n?t use yxx serie s (ex: y5v) or zxx series (ex: z5u) ty pes of cap a citor. althou gh they coul d be che ape r tha n x5r o r x7 r, yxx serie s and zxx se ri es? p e rm anen ce i s not a s g ood a s x5 r/x7 r and is easier to have problems like audio noise problem. the lifetime of a cera mic capa citor i s sho r ter if th e dc-bia s is clo s e to its maximum dc rating. fo r example, to a v out =12v application, a 25v dc capa citor shoul d ha ve a longer lifetime than a 16v dc capa cito r does, even when other characteristics of t h e s e t w o c a p a c electrolytic capa citors hav e highe r esr than what ce rami c ca pa citors do. if electrolytic ca pacito r s a r e used as output capacitors, the esr should be low enough to meet the v out ripple voltage requirement: ripple i esr out out << for exampl e, if the v ripple volta ge of a 5v output dc/d c co nverte r sho u ld be smaller tha voltage peak to peak ripple v ) ( ou t n 250mv peak-to- p eak and if the ripple cu rre nt is 0.5a, an c p a c i t o r who s e esr is << (0.25v/0.5a) &? 5 00m ? sh ould be chosen. a 680uf of esr<500 m ? capacitor can be used in this case. citors or oth e r ca pacito r s th at the e s r h i gh, the rip p le cu rrent coul 3. s t cap a cito r of the boo s t converter. the capacitor(s) is better to be x7r/x5r type. uen cy i s la rge r tha n 300khz, alth ough th e co st of o u l d be che ape r. the dc-r of the ch o ck wire sho u ld be a s low as p o ssibl e to reduce the p o w a note that th e esr of el ectrolytic ca p a citor is high ly depen dent on the tem peratu r e - th e lower th e temperature t he highe r the esr and vice versa. thi s temperatu r e depe nden ce cau s e s v out ripple p r obl e m and sy stem stability proble m sometim e s. it may need to use tantal um ca pa a r e t e m p e r a t u r e i n d e p e n d e n t f o r a p p l i c a t i ons that temperature ranges are wide. it is important to ensure th e ripple cu rre n t rating of th e output capa citor is en oug h or the capa citor migh t burn o u t duri ng ope ration. to most ele c trolytic capa cito rs, the bo dy temperatu r es sho u ld n o t be highe r than environ ment temperature plus 10 c. if the body tem peratu r e of the capa cito r i s t o o d b e h i g her than the rating of the cap a cito r. for exam ple, if the air tempe r atur e that close to the input capacitor is 45c, it is better that the body temperature is << (45c + 10c ) = 55c. e l e c t i o n o f i n p u t c a p a c i t o r it is re comm ende d to put a ce rami c ca pacito r (s) of several uf to 10uf as i n p u 4. selection of inductor it is recomm e nded to use ferrite core as the cho c k ma terial. don?t u s e iro n powd e r co re be ca u s e the co re loss will be to o high for ap plicatio ns th a t the ope ratio n f r e q an iron po wd er co r e c e r l o s s . below is an equation about the inductor value: ) 3 ( ) ( ) ( , ? sw max out out f i v , 2 , ? ? ? min in out min in where, v voltage input minimum v h value inductor l sw max out min : ) ( : ) ( : ) ( : ) ( : ) ( : , usi ng a hig h e r value ind u c tor can redu ce the po we r lo ss of the boost co nverte r. anyway, a higher valu e indu ctor often is bigger in size or ha s higher dc-r, and the higher dc-r may incre a se the inducto r power loss. shielding ind u ctor ha s bet ter emi performan ce but the dc-r is o ften higher than non-shi e ld ing indu ctors of t h e s ? = v v v l efficiency typical hz frequency switching f a current output maximum i v voltage output typical v o u t in , a m e s i z e . it is recom m ende d to adopt a n in ducto r value that the dc/dc converter will n o t transfe r fro m
lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch disco n tinue -curre nt-mo d e (dcm ) to contin ue- cu rrent-m ode (ccm) or vi se versa when v in or i out ch ange. s u c h m o d e c h a n g i n g w i l l c a u s e t h e d u t y c y c l e o f the boost dc/dc converte r becomes unstable. 5. s h an i out is ode of lowe r d r o pout voltage can im prove the sy ste m ef ficien cy. please i f i c a t i on of the schottky diode at the same time. 6. m i n i m o se t o 0%) o r t o o big (clo se to 100%). small duty cycle happen s wh en v out /v in is lo w and big dut y cycle happe ns wh en v out /v in refu lly examine wheth e r the dc/ dc conv erter u nde r d e sig n h a s n aro u nd 7 2 . 5 l a y e l e c t i o n o f f l y w heel diode an schottky diode th at th e voltage rati ng la rge r tha n 20v a nd t he current ra t i n g l a r g e r t recomme nde d. adopt a s c hottky di a l s o c h e c k t h e l e a k a g e c u r r e n t s p e c note that th e maximum workin g temp eratu r e s of m any sch o ttky diode s a r e on ly 120 c. please do ub l e check the working temperature of the schottky di ode to ensure it is within the specification. u m & m a x i m u m duty cy cle limitation pwm ics often have troub le to conve r t a v out from a v in if the duty cycle is to o s m a l l ( c l is hig h . dc/ dc conve r ter desig ners n eed to ca s u c h d u t y c y c l e l i m i t p r o b l e m , e s p e c i a l l y w h e t h e n o m i n a l v out /v in is already <1.2 or >5. note that fac t ors lik e v in deviation, com pone nt value deviation, te mperature ch ange, swit chi ng freq uen cy deviation? etc, can p u sh the duty cycl e to be much hi ghe r/lowe r than wh at we expe ct from the nomi nal v out /v in values. fo r exam ple, the duty of a 3.3v inp u t, 12v outp u t dc/ dc co nverter se em s to be % , b u t t h e a c t u a l d u ty cycle c ould be up to 80% if we inclu d e the voltage drop s of outp u t schottky, v in trace drop, v in ripple voltage drop, inductor line drop ?etc. o u t g u i d e l i n e ver. 1.2 7/10 pcb layout is an imp o rt a n t st ag e for po wer circuit, esp e ci ally the swi t ching type dc/d c convert e r that p r ovidi ng g hig h switchi ng fre q uen cy . if pcb layout is n o t ca refully d one, the bo o s t co nverte r r i o u s e m i p r o b l e m s . s e t o t h e i n d u c t o r . h a n d a c c o r d i n g t o t h e f o r m u l a o f high curre n t/volt age a nd u s i n may be unst a b l e o r c a u s e s e use wide, sh ort, and strai ght forwa r d trace s for high curr ent p a th s. about the input ca p a citors, two or more cerami c cap a citors of seve ral uf or bigg er a r e re com m ende d to b e use d . place one of th em v e ry cl ose to t he v in pin o f i c a n d g r o u n d , a n d a t l e a s t o n e a n o t h e r v e r y c l o it is very import ant to kee p the loop of the sw pin, schottky dio de, output ca p a citor , an d the gnd pin of lsp6501 a s small a s po ssible, and also minimize the lengt h of the trace s bet we en these com pone nt s, a s shown in the following fig. 1. this is because the di/d t a t t h e s e t r a c e s i s v e r y h i g dt di l v ? = the relate d volt age spikes will be very hi gh if the trace indu ct an ce is high. su ch volt age spike s not ju st cau s e e m c problems, but may interfere or even damage the ic sometimes. the mo st im port a nt is, it is better no t to use via h o les i n the lo op de scrib ed above, be ca u s e via h o les have high induct ance.
lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch ver. 1.2 8/10 a 304 v dd ss fb gnd d f l sw fre q comp r p c p2 c out c in c p1 r 1 r 2 v in v ou t c ss shd n o n / o ff t h e l o op n e e d s t o be a s s m a l l as pos si b l e. l s p 650 1 fig. 1 secon d , keep all the analo g compo nent s and sign al traces, for exa m ple the v out sense trace, far away from the noisy area s, that is, the areas ne ar ind u cto r , lsp65 01 swit ch pin , and schottky diode. if the v out s e ns e tr a c e is clo s e to the noisy a r ea, l a rge noi se m a y be co uple d into fb pin and cau s e v out value not accurate or unst able. please refer to fig. 2. a3 0 4 v dd ss f b gn d d f l sw fr e q com p r p c p 2 c ou t c in c p1 r 1 r 2 v in v out c s s s hdn on / o f f no i s y a r e a . l s p 650 1 a nal og c o m p onent s & t r ac es shoul d be f a r aw ay f r om noi sy a r ea . fig. 2 about analog ground (the ground for feedb ack re si stors, sof t st art cap a cito r , v out sensin g resi sters, and comp en satio n co mpon ent s), it is re com m ende d to u s e sh ort tra c e s to con n e c t these gro und p o int s and th e n dire ctly connect these traces to the gnd pin of t he ic. please refer to fig. 3 & fig. 4.
lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch a304 v dd ss fb gn d d f l sw fr e q comp r p c p2 c ou t c in c p1 r 1 r 2 v in v ou t c ss sh dn on/ o f f ver. 1.2 9/10 a3 0 4 v dd ss fb gn d d f l sw fre q comp r p c p2 c ou t c in c p1 r 1 r 2 v in v ou t c ss s hdn on / o ff a n a l og gr oun d i s i n dependent w i t h po w e r gro und. i t i s al so short a n d f a r aw ay f r o m n o i s y ar ea . ( g o od) lo a d 1 lo a d 2 it is b a d t o u s e othe r g r ou nd tra c e a s a n a l o g g r o u n d . it is e v e n wo r s e if t h e tr a c es a r e l o n g , c l o s e t o noi sy area o r c o nnect e d t o hi gh c u rr e n t dev i ces. (b a d ) lo ad 1 lo a d 2 l s p 650 1 l s p 650 1 f i g . 3 f i g . 4 a big g r ou nd plane (form i nput to o u t p u t) can h e lp almo st all the perfo rma n ce of the chip. beside the g r ound trace on the top layer , please use another layer as the ground layer . ordering information packag e: ms : ms o p 8 l o u tp ut vo ltage: blan k: a d j packing : a : t a pe & real t e m p eratu r e g r ade: c: - 2 0 85
l s p6501x x x x marking information msop-8 l s p650 1 lsc vy wz lo go par t id
lsp6501 1.6a, 1.3mhz, boost dc-dc converter w i th internal switch p ackage informa t ion ver. 1.2 10/10 k d g m j c p a f b i n c h e s m i l l i m e t e r s m i n t y p m a x m i n t y p m a x a 0 . 1 1 4 0.1 1 8 0 . 1 2 2 2 . 9 3 3 . 1 b 0 . 1 1 4 0.1 1 8 0 . 1 2 2 2 . 9 3 3 . 1 c 0 . 0 4 3 1 . 1 d 0.012 0.3 f 0 . 0 1 6 0 . 0 2 1 0 . 0 3 1 0 . 4 0 . 5 3 0 . 8 g 0 . 0 2 6 b s c 0 . 6 5 b s c j 0.006 0.15 k 0 - 0 . 0 0 6 0 - 0 . 1 5 m 0 o - 8 o 0 o - 8 o p 0 . 1 8 5 0 . 1 9 3 0 . 2 0 1 4 . 7 4 . 9 5 . 1

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