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ame 1 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p down dc/dc converter n t ypical application n general de scri ption the AME5296 is a high frequency synchronous ste pdown dc-dc cnverter with built intern al power mosfet s. that provide s wide 4.5v to 18v in put voltage ra nge a nd 2a continuous loa d current ca pa bility . the AME5296 ha s synchronous mode operation f or higher ef f iciency over output current loa d ra nge. the AME5296 is current mode control sche me which provide s fa st tra n sient re spon se. intern al compen sation function.n fe ature s l w ide 4.5v to 18v operating in put ra nge l 100m w /40m w low r ds(on) internal power mosfet s l proprietary switching loss reduction t e chn -ique l high efficiency synchronous mode operation l fixed 500khz switching frequency l extern al progra mma ble soft start l ocp a nd hiccup l thermal shutdown l output adjusta ble from 0.8v l rohs compli a nt a nd halogen free n application l notebook syste ms a nd i/o power l digital set t op boxe s l lcd display , tv l networking, x dsl mode m v c c b s t i n f b s s e n s w g n d a m e 5 2 9 6 c 1 2 2 u f 2 5 v c 3 1 u f e n l 1 4 . 7 u h c 2 4 7 u f r 2 1 2 . 7 k c 4 0 . 1 u f v i n 4 . 5 - 1 8 v c 4 2 2 n f v o u t 3 . 3 v 2 a r 3 3 3 k r 1 4 0 . 2 k r 4 1 0 w
ame 2 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p-down dc/dc converter n function al block di agra m 1 m e g e n r e f e r e n c e 5 0 p f 4 0 0 k 1 p f o s c i l l a t o r s s v c c i n c o m p a r a t o r o n t i m e c o n t r o l l o g i c c o n t r o l c u r r e n t l i m i t c o m p a r a t o r c u r r e n t s e n s e a m p l i f e r l s d r i v e r v c c h s d r i v e r e r r o r a m p l i f e r r s e n s w b s t g n d f b v c c r e g u l a t o r m v c c
ame 3 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p down dc/dc converter n pin configuration tsot -23-8 t op v iew AME5296-aeaxxx1. ss 2. in 3. sw 4. gnd 5. bst6. en 7. vcc 8. fb n pin de scri ption 1 3 2 6 4 5 a m e 5 2 9 6 7 8 * die attach: conductive epoxy 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 s s s o f t - s t a r t c o n t r o l i n p u t . s s c o n t r o l s t h e s o f t - s t a r t p e r i o d . c o n n e c t a c a p a c i t o r f r o m s s t o g n d t o s e t t h e s o f t - s t a r t p e r i o d . 2 i n s u p p l y v o l t a g e . t h e a m e 5 2 9 6 o p e r a t e s f r o m a + 4 . 5 v t o + 1 8 v i n p u t r a i l . c 1 i s n e e d e d t o d e c o u p l e t h e i n p u t r a i l . u s e w i d e p c b t r a c e t o m a k e t h e c o n n e c t i o n . 3 s w s w i t c h n o d e . c o n n e c t t h i s p i n t o a n e x t e r n a l l - c f i l t e r . 4 g n d s y s t e m g r o u n d . t h i s p i n i s t h e r e f e r e n c e g r o u n d o f t h e r e g u l a t e d o u t p u t v o l t a g e . f o r t h i s r e a s o n c a r e m u s t b e t a k e n i n p c b l a y o u t . s u g g e s t e d t o b e c o n n e c t e d t o g n d w i t h c o p p e r a n d v i a s . 5 b s t b o o t s t r a p f o r h i g h s i d e g a t e d r i v e r . c o n n e c t a 0 . 1 m f o r g r e a t e r c e r a m i c c a p a c i t o r f r o m b s t t o s w p i n s . 6 e n e n = 1 t o e n a b l e t h e a m e 5 2 9 6 . e n = 0 t o t u r n - o f f t h e a m e 5 2 9 6 . 7 v c c b i a s s u p p l y . d e c o u p l e w i t h a 0 . 1 m f - t o - 1 m f c a p . 8 f b f e e d b a c k i n p u t . i t i s u s e d t o r e g u l a t e t h e o u t p u t o f t h e c o n v e r t e r t o a s e t v a l u e v i a a n e x t e r n a l r e s i s t i v e v o l t a g e d i v i d e r .
ame 4 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p-down dc/dc converter n ordering information number of pins pa ck age t ype pin configuration AME5296 - x x x xxx x output v oltage a 1 . s s e : s o t - 2 x a : 8 a d j : a d j u s t a b l e l : t s o t - 2 3 - 8 ( l o w p r o f i l e ) ( t s o t - 2 3 - 8 ) 2 . i n 3 . s w 4 . g n d 5 . b s t 6 . e n 7 . v c c 8 . f b s p e c i a l f e a t u r e 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 special feature
ame 5 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p down dc/dc converter n absolute m axi mum ratings n re commended operating condition s 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 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 4 . 5 v t o 1 8 v o u t p u t v o l t a g e v o u t 0 . 8 v t o v i n - 3 v 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 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 5 5 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 1 0 0 i n t e r n a l p o w e r d i s s i p a t i o n p d 1 2 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 t s o t - 2 3 - 8 m a x i m u m u n i t - 0 . 3 t o 1 9 v - 0 . 3 v ( - 5 v f o r 1 0 n s ) t o 1 9 v ( 2 0 v f o r 5 n s ) v v s w + 6 v v - 0 . 3 t o 6 . 5 v 1 5 0 o c 2 6 0 o c s t o r a g e t e m p e r a t u r e - 6 5 t o + 1 5 0 o c v i n p a r a m e t e r j u n c t i o n t e m p e r a t u r e l e a d t e m p e r a t u r e v s w v b s t a l l o t h e r p i n s
ame 6 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p-down dc/dc converter n ele ctrical spe cif ication s v in =12v , unle ss otherwise noted. t ypical value s are at t a =25 o c. 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 s u p p l y s h u t d o w n c u r r e n t i i n v e n = 0 v 0 . 1 m a s u p p l y c u r r e n t i q v e n = 2 v , v f b = 1 v , v s s = 3 v 0 . 7 m a h i g h s i d e s w i t c h o n - r e s i s t a n c e r d s ( o n ) 1 v b s t - s w = 5 v 1 0 0 m w l o w s i d e s w i t c h o n - r e s i s t a n c e r d s ( o n ) 2 v c c = 5 v 4 0 m w l o a d s i d e s w i t c h l e a k a g e c u r r e n t s w l k g v e n = 0 v , v s w = 1 2 v 0 . 1 5 m a s w i t c h c u r r e n t l i m i t 2 . 8 a o s c i l l a t o r f r e q u e n c y f o s c 1 v f b = 0 . 7 5 v 5 0 0 k h z f o l d - b a c k f r e q u e n c y f f b v f b < 4 0 0 m v 0 . 2 5 f s w m a x i m u m d u t y c y c l e d m a x v f b = 7 0 0 m v 9 0 9 5 % f e e d b a c k v o l t a g e v f b - 4 0 o c < t a < 8 5 o c - 2 % 8 0 0 2 % m v f e e d b a c k c u r r e n t i f b v f b = 8 0 0 m v 1 0 5 0 n a e n r i s i n g t h r e s h o l d v e n _ r i s i n g 1 . 2 1 . 4 1 . 6 v e n f a l l i n g t h r e s h o l d v e n _ f a l l i n g 1 . 1 1 . 2 5 1 . 4 v v e n = 2 v 2 m a v e n = 0 v 0 m a e n t u r n o f f d e l a y e n t d - o f f 8 m s i n p u t u n d e r v o l t a g e l o c k o u t t h r e s h o l d v u v l o 3 . 6 v i n p u t u n d e r v o l t a g e l o c k o u t h y s t e r e s i s d v u v l o 6 0 0 m v v c c r e g u l a t o r v c c 5 v v c c l o a d r e g u l a t i o n i c c = 5 m a 5 % 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 h y s t e r e s i s 2 0 o c e n i n p u t c u r r e n t i e n
ame 7 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p down dc/dc converter n detailed de scri pti ion internal v cc regulator the internal v cc regulator is adjusted 5.0v to provide power to the internal circuits from input voltage v in . in order to maintain the v cc voltage sta bly , a 0.1 m f-to-1 m f cera mic ca pa citor is re commended. enable and soft startthe en pin provides electrical on/off control of the regu- lator . when the en pin voltage exceeds the lockout thre shold voltage, the regulator starts to operate a nd the soft start begin s to charge the extern al ca pa citor . if the en pin voltage is pulled below the lockout threshold volt-age, the regulator stops switching a nd the soft start re- sets. conne cting the en pin to ground or to a ny voltage le ss tha n 1.2v will disa ble the regulator a nd a ctivate the shutdown mode. t o li mit the start-up inrush current, a soft-start circuit is used to ra mp up the reference voltage from 0v to its f in al value line arly . the soft start ti me ca n be calculated a s f ollows: u nder v oltage lockout (uvlo) the AME5296 incorporate s a n under voltage lockout cir- cuit to keep the device disabled when the input voltage v in is below the uvlo start thre shold voltage. during power- ing up, the intern al circuits are held in a ctive a nd the soft start is grounded until the input voltage v in exceeds the uvlo start threshold voltage. once the uvlo start thresh-old voltage is re a ched, the soft start is a ctivated a nd the device begins to operate. the device operates until theinput voltage v in falls below the uvlo stop threshold volt- age. the typical hysteresis in the uvlo comparator is650mv . s s s s s s i c 0 . 8 t = thermal shutdown the AME5296 prote cts itsel f from overhe ating with a n internal thermal shutdown circuit. if the junction tempera-ture exceeds the thermal shutdown threshold, the voltage reference is grounded a nd the shutdown mode is a ctivated. the AME5296 is re started under control of the soft start automatically when the junction temperature drops 20 o c below the thermal shutdown threshold. over-current protection and hiccup modethe over-current limiting is implemented by cycle-by- cycle monitoring the current through the high side mosfet . if the pe a k current exceeds the over-current li mit thre sh- old, the high side mosfet is turned off. when the feed-ba ck voltage v fb drops below 0.4v , the oscillator frequency is reduced to about 1/4 of the normal frequency to ensurethat the inductor current ha s more ti me to de cay , thereby preventing run away . me a nwhile, the AME5296 enters hic- cup mode, the average short circuit current is greatly re-duced to allevi ate the thermal issue a nd to prote ct the regulator . entern al bootstra p circuit the extern al bootstra p circuit contain s a ca pa citor a nd a re sistor . a bootstra p ca pa citor provide s power f or the high side mosfet driver . in order to supply the ac current a nd maintain the bst -sw voltage sta bly at the switching con- dition of the high side mosfet , a 1 m f low esr cera mic ca pa citor is re commended. the bootstra p re sistor which sugge sts pla cing 10 w is utilized to reduce switching spike voltage a nd noise.
ame 8 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p-down dc/dc converter n application inf ormation inductor selectionfor most a pplication s, the inducta nce ra nge is chosen ba sed on the de sired ri pple current. a larger inducta nce reduce s ri pple current; me a nwhile, the output ri pple volt- age de cre a se s. 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 maxi mum loa d current. the inducta nce value ca n be cal- culated by: where f is the oscillator frequency , v in is the in put volt- age, v out is the output voltage, a nd d i 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 current, cal- culated by: where i load is the load current. the choice of which style inductor to use mainly depends on the price vs. sizerequire ments a nd a ny emi con straints. in put ca pa citor the input current to the buck converter is discontinu- ous; theref ore a n in put ca pa citor is required to supply the ac current while maintaining the dc in put voltage. in or- der to prevent large voltage drop, a low esr ca pa citors is re commended f or the be st perf orma nce. cera mic ca pa ci- tors are preferred, but ta ntalum or low-esr ele ctrolytic ca pa citors will also be sugge sted. choose x5r or x7r diele ctrics when using cera mic ca pa citors. since the in- put ca pa citor a bsorbs the in put switching current, it re- quire s a n a dequate ri pple current rating. the rms current in the in put ca pa citor ca n be e sti mated by: - = i n o u t l o u t v v 1 i f v l - + = i n o u t l o u t l o a d l p e a k v v 1 i f 2 v i i - = i n o u t i n o u t l o a d c i n v v 1 v v i i at v in = 2v out , where i cin = i load /2 is the worst-ca se condition occurs. for si mplif ication, use a n in put ca pa ci- tor 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. 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 c in is the in put ca pa cita nce value. output ca pa citor the output ca pa citor (c out ) is required to maintain the dc output voltage. cera mic, ta ntalum, or low esr ele c- trolytic ca pa citors are re commended. low esr ca pa ci- tors 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 c out is the output ca pa ci- ta nce value. when using cera mic ca pa citors, the i mpeda nce at the switching frequency is domin ated by the ca pa cita nce which is the main cause for the output voltage ripple. for simpli-f ication, the output voltage ri pple ca n be e sti mated by: - = i n o u t i n o u t i n l o a d i n v v 1 v v f c i v + - = o u t e s r i n o u t o u t o u t c f 8 1 r v v 1 l f v v - = i n o u t o u t 2 o u t o u t v v 1 c l f 8 v v
ame 9 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p down dc/dc converter 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: setting the output v oltage the output voltage is using a re sistive voltage divider conne cted from the output voltage to feedba ck pin. it divide s the output voltage down to the feedba ck voltage by the ratio: the output voltage is: e s r i n o u t o u t o u t r v v 1 l f v v - = 2 1 2 o u t f b r r r v v + = 2 2 1 o u t r r r 8 . 0 v + = n t ypical application circuits v o u t ( v ) r 1 ( k w ) r 2 ( k w ) r 3 ( k w ) l ( m h ) c i n ( m f ) c o u t ( m f ) 1 . 0 2 0 . 5 8 2 . 0 8 2 1 . 5 2 2 2 2 x 2 1 . 2 3 0 . 1 6 0 . 4 8 2 1 . 5 2 2 2 2 x 2 1 . 8 4 0 . 2 3 2 . 4 5 6 2 . 2 2 2 2 2 x 2 2 . 5 4 0 . 2 1 9 . 1 3 3 3 . 3 2 2 2 2 x 2 3 . 3 4 0 . 2 1 2 . 7 3 3 4 . 7 2 2 2 2 x 2 5 . 0 4 0 . 2 7 . 6 8 3 3 6 . 8 2 2 2 2 x 2 v c c b s t i n f b s s e n s w g n d a m e 5 2 9 6 c 3 1 u f r e n 2 1 0 k c 6 1 5 p f r 5 0 w c 4 0 . 1 u f r 4 1 0 w r e n 1 1 8 k c i n 2 n s c i n 1 2 2 u f c 5 2 2 n f l 1 4 . 7 u h r 1 4 0 . 2 k r 3 3 3 k r 2 1 2 . 7 k c o u t 1 2 2 u f c o u t 2 2 2 u f v i n 4 . 5 v ~ 1 8 v v o u t 3 . 3 v / 2 a
ame 10 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p-down dc/dc converter n chara cterization curve loa d t ra n sient output v oltage ri pple power on from in put v oltage power on from in put v oltage time(200 m f /div) i l (1a/div) v out (200mv/div) time(2 m s /div) i l (2a/div) v out (20mv/div) v in(ac) (100mv/div) v sw (10v/div) time(5 ms /div) time(5 ms /div) i l (2a/div) v out (2v/div) v in (5v/div) v sw (5v/div) i l (2a/div) v out (2v/div) v in (5v/div) v sw (5v/div) v in =12v , v out =3.3v , i out =0.5~2a v in =12v , v out =3.3v , i out =2a v in =12v , v out =3.3v i out =0a v in =12v , v out =3.3v i out =2a power on from en time(5 ms /div) i l (2a/div) v out (2v/div) v en (5v/div) v sw (5v/div) v in =12v , v out =3.3v i out =0a power on from en i l (2a/div) v out (2v/div) v en (5v/div) v sw (5v/div) time(5 ms /div) v in =12v , v out =3.3v i out =2a c4 c4 c3 c2 c1 c 3 c4 c3 c2 c1 c1 c4 c3 c2 c1 c2 c3 c4 c1 c2 c3 c4
ame 11 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p down dc/dc converter power off from in put v oltage power off from in put v oltage i l (2a/div) v out (2v/div) v in (5v/div) v sw (5v/div) time(50 ms /div) i l (2a/div) v out (2v/div) v in (5v/div) v sw (5v/div) time(5 ms /div) v in =12v , v out =3.3v , i out =0a v in =12v , v out =3.3v , i out =2a power off from en i l (2a/div) v out (2v/div) v en (5v/div) v sw (5v/div) time(2 s /div) v in =12v , v out =3.3v , i out =0a power off from en i l (2a/div) v out (2v/div) v en (5v/div) v sw (5v/div) time(5m s /div) v in =12v , v out =3.3v , i out =2a short circuit entry short circuit recovery i l (5a/div) v ss (1v/div) v out (1v/div) v sw (10v/div) time(5m s /div) i l (5ad/iv) v sw (10v/div) v out (1v/div) v ss (1v/div) time(5m s /div) v in =12v , v out =3.3v , i out =0a v in =12v , v out =3.3v , i out =0a c4 c3 c2 c1 c4 c3 c2 c1 c4 c3 c2 c1 c4 c3 c2 c1 c4 c3 c2 c1 c4 c3 c2 c1
ame 12 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p-down dc/dc converter efficiency output current (a) efficiency (%) efficiency output current (a) efficiency (%) efficiency efficiency (%) output current (a) v o u t = 5 v , i o u t = 0 ~ 2 a 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0 1 8 v 1 2 v v o u t = 3 . 3 v , i o u t = 0 ~ 2 a 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0 1 2 v 1 8 v 5 v 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 0 . 0 0 . 5 1 . 0 1 . 5 2 . 0 1 2 v 5 v 1 8 v v o u t = 1 . 2 v , i o u t = 0 ~ 2 a
ame 13 AME5296 rev . a.05 2a, 18v , 500khz synchronous ste p down dc/dc converter n t a pe a nd reel di men sion tsot -23-8 carrier t a pe, number of components per reel a nd reel size n pa ck age di men sion s i d e v i e w l t o p v i e w e 1 d e e 1 f r o n t v i e w a 2 p i n 1 b e c 0 . 2 5 a a 1 tsot -23-8 p i n 1 w p 0 a m e a m e p 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 i t c h ( p 0 ) p a r t p e r f u l l r e e l r e e l s i z e t s o t - 2 3 - 8 8 . 0 0 . 1 m m 4 . 0 0 . 1 m m 4 . 0 0 . 1 m m 3 0 0 0 p c s 1 8 0 1 m m
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. , october 2014 document: a018a-ds5296-a.05 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

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