View AME5235_8374725.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

ame 1 AME5235 rev . a.02 40v 3.5a buck converter n general de scri ption the AME5235 is a spe cif ic 40v hv buck converter supports a n output voltage ra nge of 0.8v to 12v at 200khz switching frequency . protection features include under voltage protection, over voltage protection, current limit, thermal shutdown,a nd short circuit prote ction. the device is availa ble in sop-8/pp pa ck age with exposed pa d f or low thermal re sista nce. n fe ature s n application l car charger l w all ada pter l 40v maximum rating for input power l 200khz switching frequency l internal soft start l uvp , in put/output ovp , otp , scp l a vaila ble in sop-8/pp pa ck age l rohs compli a nt a nd halogen free n function al block di agra m n t ypical application e m i c o n t r o l p w m c o n t r o l l e r g n d c o m p i n f b 0 . 8 v b s s w o s c i l l a t o r v r e f & s / d c o n t r o l a m e 5 2 3 5 s k 3 4 l 1 4 7 u h s w f b g n d r 3 8 . 2 k c 4 3 . 3 n f c o m p i n c 2 4 7 0 u f c 3 2 2 n f v i n = 8 v ~ 4 0 v b s r 1 1 1 0 k r 2 2 0 k v b u s g n d c 1 4 7 u f r 4 1 0 w d 1 c 5 o p t i o n a l
ame 2 AME5235 rev . a.02 40v 3.5a buck converter n pin configuration sop-8/pp t op v iew AME5235-azaadj1. in 2. comp 3. nc 4. nc 5. fb 6. gnd 7. sw 8. bs * die attach: conductive epoxy n pin de scri ption 1 3 2 4 g n d 5 6 7 8 p i n n o . p i n n a m e p i n d e s c r i p t i o n 1 i n i n p u t p o w e r . 2 c o m p c o m p e n s a t i o n n o d e . 3 , 4 n c n o c o n n e c t i o n . 5 f b f e e d b a c k i n p u t . 6 g n d g r o u n d . 7 s w p o w e r s w i t c h i n g o u t p u t 8 b s h i g h s i d e . g a t e d r i v e b o o s t i n p u t . 9 e x p o s e d p a d g r o u n d .
ame 3 AME5235 rev . a.02 40v 3.5a buck converter n ordering information number of pins pa ck age t ype pin configuration AME5235 - x x x xxx output v oltage a 1 . i n z : s o p / p p a : 8 a d j : a d j u s t a b l e ( s o p - 8 / p p ) 2 . c o m p 3 . n c 4 . n c 5 . f b 6 . g n d 7 . s w 8 . b s p i n c o n f i g u r a t i o n p a c k a g e t y p e n u m b e r o f p i n s o u t p u t v o l t a g e
ame 4 AME5235 rev . a.02 40v 3.5a buck converter n absolute m axi mum ratings n re commended operating condition s p a r a m e t e r s y m b o l r a t i n g u n i t i n p u t v o l t a g e v i n 8 t o 4 0 o u t p u t v o l t a g e v o u t 0 . 8 t o 1 2 j u n c t i o n t e m p e r a t u r e r a n g e t j - 4 0 t o + 1 2 5 a m b i e n t t e m p e r a t u r e r a n g e t a - 4 0 t o + 8 5 o c v n thermal information * me a sure q jc on ba ck side center of molding compound if ic ha s no ta b. ** mil-st d-202g 210f p a r a m e t e r p a c k a g e d i e a t t a c h s y m b o l m a x i m u m u n i t t h e r m a l r e s i s t a n c e * ( j u n c t i o n t o c a s e ) q j c 1 9 t h e r m a l r e s i s t a n c e ( j u n c t i o n t o a m b i e n t ) q j a 8 4 p o w e r d i s s i p a t i o n p d 1 4 5 0 m w 2 6 0 o c l e a d 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 ) * * c o n d u c t i v e e p o x y o c / w s o p - 8 / p p m a x i m u m u n i t - 0 . 3 v t o 4 0 v - 1 t o v i n + 1 v v s w - 0 . 3 t o v s w + 7 v - 0 . 3 v t o 7 v 2 0 0 0 v 1 5 0 o c - 6 5 t o + 1 5 0 o c h b m 2 k v m m 1 5 0 v e s d c l a s s i f i c a t i o n s t o r a g e t e m p e r a t u r e i n p u t v o l t a g e p a r a m e t e r s w i t c h v o l t a g e b o o s t s w i t c h v o l t a g e a l l o t h e r p i n s e l e c t r o s t a t i c d i s c h a r g e ( h b m ) j u n c t i o n t e m p e r a t u r e
ame 5 AME5235 rev . a.02 40v 3.5a buck converter n ele ctrical spe cif ication s t ypical value s v in =12v with typical t a =25 o c, unle ss otherwise spe cif ied. p a r a m e t e r s y m b o l t e s t c o n d i t i o n m i n t y p m a x u n i t s i n p u t v o l t a g e o p e r a t i n g r a n g e v i n 8 4 0 v v i n u v l o r i s i n g t h r e s h o l d v o l t a g e v u v l o i n p u t v o l t a g e r i s i n g 7 v v i n u v l o h y s t e r e s i s v u v l o _ y h s i n p u t v o l t a g e f a l l i n g 1 v s t a n d b y c u r r e n t v o u t = 5 v , n o l o a d 3 m a f e e d b a c k v o l t a g e v f b 0 . 8 v f e e d b a c k v o l t a g e a c c u r a c y d v f b - 1 . 5 + 1 . 5 % i n t e r n a l s o f t s t a r t t i m e t s s 1 0 m s h i t h s i t e s w i t c h o n - r e s i s t a n c e r d s ( o n ) _ h i 1 2 0 m w h i g h s i t e s w i t c h c u r r e n t l i m i t i c l _ h i 4 . 5 a m a x . d u t y c y c l e d m a x 8 5 % s w i t c h i n g f r e q u e n c y f o s c v f b = 0 . 8 v 1 7 5 2 0 0 2 2 5 k h z t h e r m a l s h u t d o w n t s d 1 5 0 o c t h e r m a l s h u t d o w n h y s t e r e s i s d t s d 2 0 o c o u t p u t o v p v o v - o u t v o u t x 1 . 0 6 v o u t x 1 . 1 6 v i n p u t o v p v o v - i n 3 2 3 5 4 0 v i n p u t o v p h y s t e r e s i s 2 v s h o r t c u r r e n t l i m i t 2 a
ame 6 AME5235 rev . a.02 40v 3.5a buck converter u nder v oltage lockout (uvlo) the AME5235 incorporate s a n under voltage lockout circuit to keep the device disabled when v in (the input voltage) is below the uvlo rising threshold voltage. oncethe uvlo rising thre shold voltage is re a ched,the device start-up begins. the device operates until v in falls below the uvlo falling threshold voltage. the typical hyster-e sis in the uvlo comparator is 1v . over v oltage prote ction the AME5235 ha s in put a nd output over-voltage pro- te ction s. the thre sholds of in put a nd output ovp circuit include are typica pl 35v a nd mini mum 106% x v out , re- spe ctively . once the in put voltage or output voltage is higher tha n the thre shold, the high-side mosfet is turned off. when the input voltage or output voltage drops lowertha n the thre shold, the high-side mosfet will be en- abled again. over current protectionthe AME5235 cycle-by-cycle li mits the pe a k inductor current to prote ct e mbedded switch from da me age. high- side switch current limiting is implemented by monitor-ing the current through the high side mosfet . thermal shutdownthe AME5235 prote cts itsel f from overhe ating with a n internal thermal shutdown circuit. if the junction tempera-ture exceeds the thermal shutdown trip point, the high- side mosfet is turned off. the part is restarted when the junction temperature drops 20 o c below the thermal shutdown trip point setting the output v oltage the output voltage is using a resistive voltage divider connected from the output voltage to fb. it divides theoutput voltage down to the feedba ck voltage by the ratio: 2 1 2 r r r v v o u t f b + = n detailed de scri ption the output voltage is:inductor selection the inductor is required to supply conta nt current to the load while being driven by the switched input voltage.a larger value inductor will have a larger physical size a nd higher serie s re sista nce. it will re sult in le ss ri pple current that will in turn result in lower output ripple volt-age. m a ke sure that the pe a k inductor current is below the maxi mum switch current li mit. determine inducta nce is to allow the pe a k-to-pe a k ri pple current to be a pproxi- mately 30% of the maximum load current. the induc-ta nce value ca n be calculated by: - d = i n o u t l s o u t v v i f v l 1 where f s is the switching frequency , v in is the in put voltage, v out is the output voltage, a nd di l is the pe a k- to-pe a k inductor ri pple current. choose a n inductor that will not saturate under the maxi mum inductor pe a k cur- rent, calculated by: where i load is the load current. the choice of which style inductor to use mainly depends on the price vs.size require ments a nd a ny emi con straints. in put ca pa citor the input current to the step-down converter is discon- tinuous, theref ore a ca pa citor is required to supply the ac current while maintaining the dc in put voltage. use low esr ca pa citors f or the be st perf orma nce. cera mic ca pa citors are preferred, but ta ntalum or low-esr ele c- trolytic ca pa citors will also be sugge sted. choose x5r or x7r diele ctrics when using cera mic ca pa citors. 2 2 1 8 . 0 r r r v o u t + = - + = i n o u t s o u t l o a d l p k v v l f v i i 1 2
ame 7 AME5235 rev . a.02 40v 3.5a buck converter since the in put ca pa citor (c1) a bsorbs the in put switch- ing current, it require s a n a dequate ri pple current tating. the rms current in the in put ca pa citor ca n be e si mated by: at v in =2v out , where i c1 = i load /2 is the worst-ca se con- dition occurs. for si mplif ication, use a n in put ca pa citor with a rms current rating gre ater tha n hal f of the maxi- mum loa d current. when using cera mic ca pa citors, ma ke sure that they have enough ca pa cita nce to provide suf f i- cient charge to prevent excessive voltage ripple at input.when using ele ctrolytic or ta ntalum ca pa citors, a high quality , small cera mic ca pa citor , i.e. 0.1 m f , should be pla ced a s close to the ic a s possible. the in put voltage ri pple f or low esr ca pa citors ca n be e sti mated by: where c1 is the in put ca pa cita nce value. output ca pa citor the output ca pa citor (c2) is required to maintain the dc output voltage. cera mic, ta ntalum, or low esr ele ctrolutic ca pa citors are re commended. low esr ca- pa citors are preferred to kee p the output voltage ri pple low . the output voltage ri pple ca n be e sti mated by: where r esr is the equivalent serie s re sista nce (esr) value of the output ca pa citor a nd c2 is the output ca pa ci- ta nce value. when using cera mic ca pa citors, the i mpa nda nce at the switching frequency is domin ated by the ca pa cita nce which is the main cause for the output voltage ripple. forsi mplif ication, the output voltage ri pple ca n be e sti mated by: - = i n o u t i n o u t s l o a d c v v v v f c i i 1 1 1 when using ta ntalum or ele ctrolytic ca pa citors, the esr domin ate s the i mpeda nce at the switching frequency . for si mplif ication, the output ri pple ca n be a pproxi mated to: the chara cteristics of the output ca pa citor also af fe ct the stability of the regulation system. rectifier diodeuse a schottky diode a s the re ctif ier to conduct cur- rent when the high-side mosfet is turned off. theschottky diode must have current rating higher tha n the maxi mum output current a nd a reverse voltage rating higher tha n the maxi mum in put voltage. compensation componentsAME5235 ha s current mode control f or e a sy compen- sation a nd fa st tra n sient re spon se. the syste m sta bility a nd tra n sient re spon se are controlled through the comp pin. comp is the output of the intern al tra n sconducta nce error a mplif ier . a serie s ca pa citor-re sistor combin ation sets a pole-zero combin ation to govern the chara cteris- tics of the control syste m. the dc gain of the voltage feedba ck loop is given by: where v fb is the feedba ck voltage (0.8v), a vea is the error a mplif ier voltage gain, g cs is the current sen se tra n sconducducta nce a nd r load is the loa d re sistor value. the syste m ha s two pole s of i mporta nce. one is due to the output ca pa citor a nd the loa d re sistor , a nd the other is due to the compa n sation ca pa citor (c4) a nd the output re sistor of the error a mplif ier . the se pole s are located at: - = d i n o u t s o u t o u t v v c l f v v 1 2 8 2 + - = d 2 8 1 1 c f r v v l f v v s e s r i n o u t s o u t o u t e s r i n o u t s o u t o u t r v v l f v v - = d 1 o u t f b e a c s l o a d v d c v v a g r a = - = i n o u t i n o u t l o a d c v v v v i i 1 1 v e a e a p a c g f = 4 2 1 p l o a d p r c f = 2 2 1 2 p
ame 8 AME5235 rev . a.02 40v 3.5a buck converter where g ea is the error a mplif ier tra n sconducducta nce. the syste m ha s one zero of i mporta nce, due to the com- pen sation ca pa citor (c4) a nd the compen sation re sistor (r3). this zero is located at: the syste m may have a nother zero of i mporta nce, if the output ca pa citor ha s a large ca pa cita nce a nd/or a high esr value. the zero, due to the esr a nd ca pa cita nce of the output ca pa citor , is located at: in this ca se, a third pole set by the se cond compen sa- tion ca pa citor (c5) a nd the compen sation re sistor (r3) is used to compensate the effect of the esr zero on theloop gain. this pole is located at: the goal of compen sation de sign is to sha pe the con- verter tra n s fer function to get a de sired loop gain. the syste m crossover frequency where the feedba ck loop ha s the unity gain is i mporta nt. lower crossover frequencie s re sult in slower line a nd loa d tra n sient re spon se s, while higher crossover frequencies could cause system insta-bility . a good sta ndard is to set the crossover frequency below one-tenth of the switching frequency . t o opti mize the compensation components, the following procedureca n be used. 1. choose the compensation resistor (r3) to set the de sired crossover frequency . determine r3 by the following equation:where f c is the desired crossover frequency which is typically below one tenth of the switching frequency . 3 4 2 1 1 r c f z = p e s r e s r r c f = 2 2 1 p 3 5 2 1 3 r c f p = p 2. choose the compen sation ca pa citor (c4) to a chieve the de sired pha se margin. for a pplication s with typical inductor values, setting the compensation zero (f z1 ) be- low one-forth of the crossover frequency provides suffi-cient pha se margin. determine c4 by the floolwing equation:where r3 is the compen sation re sistor . 3. determine if the se cond compen sation ca pa citor (c5) is required. it is required if the esr zero of the outputca pa citor is located at le ss tha n hal f of the switching frequency , or the f ollowing relation shi p is valid: if this is the ca se, then a dd the se cond compen sation ca pa citor (c5) to set the pole f p3 at the location of the esr zero. determine c5 by the equation: f b o u t c s e a c f b o u t c s e a c v v g g f c v v g g f c r < = 1 . 0 2 2 2 2 3 c f r c > 3 2 4 4 p 2 2 2 1 s e s r f r c < p 3 2 5 r r c c e s r =
ame 9 AME5235 rev . a.02 40v 3.5a buck converter pc board layout guidancewhen laying out the printed circuit board, the following checklist should be uesd to ensure proper operation of the ic. 1) arra nge the power components to reduce the ac loop size con sisting of c in , in pin, sw pin a nd the sckottky diode. 2) pla ce in put de coupling cera mic ca pa citor c in a s close to in pin a s possible. c in is conne cted power gnd with vi a s or short a nd wide path. 3) return fb a nd comp to sign al gnd pin, a nd conne ct the singal gnd to power gnd at a single point f or the be st noise i mmunity . conne ct exposed pa d to power ground copper are a with copper a nd vi a s. 4) use copper pla ne f or power gnd f or be st he at disspation a nd noise i mmunity . 5) ple a se feedba ck re sistor close to fb pin. t op layer bottom layer
ame 10 AME5235 rev . a.02 40v 3.5a buck converter n ra di ated emi data (v ertical) n ra di ated emi data (horizontal)
ame 11 AME5235 rev . a.02 40v 3.5a buck converter n chara cterization curve efficiency vs. output current power on from v in full load ripple loa d t ra n sient re spon se power off from v in o u t p u t c u r r e n t ( a ) e f f i c i e n c y ( % ) 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 1 0 0 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0 2 . 5 3 . 0 3 . 5 loa d t ra n sient re spon se 0 . 5 a t o 1 a 1 a t o 1 . 5 a
ame 12 AME5235 rev . a.02 40v 3.5a buck converter n chara cterization curve (contd.) 0a short 3.5a short loa d t ra n sient re spon se i l (1a/div) v out (5v/div) v sw (10v/div) time(200 m s /div) time(100 m s /div) i l (2a/div) v out (5v/div) v sw (10v/div) 1 . 5 a t o 2 . 4 a
ame 13 AME5235 rev . a.02 40v 3.5a buck converter n chara cterization curve frequency vs. t e mperature v fb vs t e mperature sta nby current vs. t e mperature 0 . 7 8 0 . 7 9 0 . 8 0 0 . 8 1 0 . 8 2 - 4 0 - 2 0 0 2 0 4 0 6 0 8 0 1 0 0 t e m p e r a t u r e ( c ) v f b ( v ) 0 . 0 0 1 . 0 0 2 . 0 0 3 . 0 0 4 . 0 0 5 . 0 0 - 4 0 - 2 0 0 2 0 4 0 6 0 8 0 1 0 0 t e m p e r a t u r e ( c ) s t a n d b y c u r r e n t ( m a ) 1 0 0 . 0 1 5 0 . 0 2 0 0 . 0 2 5 0 . 0 3 0 0 . 0 - 4 0 - 2 0 0 2 0 4 0 6 0 8 0 1 0 0 t e m p e r a t u r e ( c ) f r e q u e n c y ( k h z ) in put ovp vs. t e mperature 3 0 . 0 3 1 . 0 3 2 . 0 3 3 . 0 3 4 . 0 3 5 . 0 3 6 . 0 3 7 . 0 3 8 . 0 3 9 . 0 4 0 . 0 - 4 0 - 2 0 0 2 0 4 0 6 0 8 0 1 0 0 t e m p e r a t u r e ( c ) i n p u t o v p ( v )
ame 14 AME5235 rev . a.02 40v 3.5a buck converter n t a pe a nd reel di men sion sop-8/pp carrier t a pe, number of components per reel a nd reel size p i n 1 w p a m e a m e p a c k a g e c a r r i e r w i d t h ( w ) p i t c h ( p ) p a r t p e r f u l l r e e l r e e l s i z e s o p - 8 / p p 1 2 . 0 0 . 1 m m 4 . 0 0 . 1 m m 2 5 0 0 p c s 3 3 0 1 m m b e e e 2 c f r o n t v i e w s i d e v i e w t o p v i e w d 1 e 1 l 1 d a 1 a a 2 p i n 1 n pa ck age di men sion sop-8/pp m i n m a x m i n m a x a 1 . 3 5 0 1 . 7 5 0 0 . 0 5 3 0 . 0 6 9 a 1 0 . 0 0 0 0 . 2 5 0 0 . 0 0 0 0 . 0 1 0 a 2 1 . 2 5 0 1 . 6 5 0 0 . 0 4 9 0 . 0 6 5 c 0 . 1 0 0 0 . 2 5 0 0 . 0 0 4 0 . 0 1 0 e 3 . 7 5 0 4 . 1 5 0 0 . 1 4 8 0 . 1 6 3 e 1 5 . 7 0 0 6 . 3 0 0 0 . 2 2 4 0 . 2 4 8 l 1 0 . 3 0 0 1 . 2 7 0 0 . 0 1 2 0 . 0 5 0 b 0 . 3 1 0 0 . 5 1 0 0 . 0 1 2 0 . 0 2 0 d 4 . 7 2 0 5 . 1 2 0 0 . 1 8 6 0 . 2 0 2 e q q q q 0 o 8 o 0 o 8 o e 2 1 . 9 4 0 2 . 6 0 0 0 . 0 7 6 0 . 1 0 2 d 1 1 . 9 4 0 3 . 5 0 0 0 . 0 7 6 0 . 1 3 8 1 . 2 7 0 b s c 0 . 0 5 0 b s c s y m b o l s m i l l i m e t e r s i n c h e s
life support policy: the se products of ame, inc. are not authorized f or use a s critical components in life-support device s or syste ms, without the expre ss written a pproval of the pre sident of ame, inc. ame, inc. re serve s the right to ma ke cha nge s in the circuitry a nd spe cif ication s of its device s a nd a dvise s its customers to obtain the late st version of releva nt inf ormation. ? ame, inc. , june 2013 document: a016a-ds5235-a.02 corporate he a dquarter ame, inc.8f , 12, w enhu st., ne i-hu t ai pe i 1 14, t aiwa n . t el: 886 2 2627-8687 fax: 886 2 2659-2989 www .a me.com.tw e-m ail: sale s@a me.com.tw

▲Up To Search▲

Price & Availability of AME5235

	To Download AME5235 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .