power management 1 www.semtech.com sc1418 600khz single cell step-up dc/dc converter preliminary features applications revision 09/2001 typical application circuit description the sc1418 is a fixed off time, current mode, step up dc/ dc converter aimed primarily at single cell applications. by using synchronous rectification conversion efficiencies of greater than 90% are achievable. the fixed off time is varied with input to output ratio to achieve constant frequency operation for a range of input voltages. the chip is initially powered from the input voltage. once the output is established, the chip is powered from the output. start up is guaranteed from a 0.9v input supply with loads less than 5ma. the low battery monitor, including 200mv reference circuit, remains active when the part is shut down. u pseudo fixed off time, current mode control u bootstrapped supply voltage u constant frequency over wide load range u fixed 3.3v output u 180ma output load at v in = 1.2v u synchronous rectification, 550m w on chip pmos u 350m w on-chip power nmos u up to 92% efficient at 100ma load u guaranteed startup at 0.9v u low battery monitor function u msop-8 package 20k 100pf 10uf 270k 1m gnd 1500pf 0.9v to 3.0v vout 10uf sc1418is 3 1 2 7 4 8 5 6 lbo vout gnd en comp lx vin lbi en 1m 10uh lbo u pda, mp3, pager u cordless telephone u hand held gps
2 ? 2001 semtech corp. www.semtech.com power management sc1418 preliminary r e t e m a r a pl o b m y sm u m i x a ms t i n u e g a t l o v y l p p u s t u p n iv n i 7v e g a t l o v t u p t u ov t u o 7v t u p n i x lv x l 7v t u p n i i b lv i b l 2 o t 3 . 0 -v t u p n i n ev n e 7 o t 3 . 0 -v t u p t u o o b lv o b l 7 o t 3 . 0 -v t u p t u o p m o cv p m o c 2 o t 3 . 0 -v e g n a r e r u t a r e p m e t t n e i b m a g n i t a r e p ot a 5 8 o t 0 4 -c e r u t a r e p m e t n o i t c n u j g n i t a r e p ot j 5 2 1c e r u t a r e p m e t e g a r o t st g t s 0 5 1 o t 5 6 -c s 0 1 ) g n i r e d l o s ( e r u t a r e p m e t d a e lt d a e l 0 0 3c t n e i b m a o t n o i t c n u j e c n a t s i s e r l a m r e h t ) 1 ( q a j 5 9w / c e s a c o t n o i t c n u j e c n a t s i s e r l a m r e h t q c j 9 3w / c note: (1) 1 square inch of fr4, double sided, 1oz. minimum copper weight. absolute maximum ratings
3 ? 2001 semtech corp. www.semtech.com power management sc1418 preliminary unless specified, v in = 1.2v, v out = 3.3v; t a = -40 to 85 o c. r e t e m a r a pl o b m y ss n o i t i d n o cn i mp y tx a ms t i n u e g a t l o v t u p n iv n i l a n o i t a r e p o8 . 0v t u o v 3 . 0 - v i . p u t r a t s t u o t ; a m 5 < j c 0 0 1 o t 0 =9 . 0 e g a t l o v t u p t u ov t u o i t u o a m 0 0 1 =3 1 . 30 3 . 37 4 . 3v t n e r r u c t u p t u o m u m i x a mi t u o v t u o v 3 . 3 = v n i v 9 . 0 =7 2 1 a m v n i v 2 . 1 =2 8 1 v n i v 5 . 1 =0 4 2 t n e r r u c d a o l p u - t r a t si t r a t s v n i v 2 . 1 =0 5a m e c n a t s i s e r n o h c t i w s r e w o p s o m nr ) n o ( s d 0 9 10 5 3m w e c n a t s i s e r n o h c t i w s r e w o p s o m pr ) n o ( s d 0 8 20 5 5m w e g a k a e l h c t i w s r e w o p s o m nv ; v 5 . 5 = d n g - x l n e v 0 =1 . 05 1 m a e g a k a e l h c t i w s r e w o p s o m pv t u o v ; v 5 . 5 = x l - n e v 0 =1 . 00 1 m a t i m i l t n e r r u c h c t i w s r e w o pi t i m i l 7 . 01 3 . 1a e c n a t c u d n o c s n a r t r e i f i l p m a r o r r em gl d p m o c a 2 =0 70 4 10 4 2s n i a g r e i f i l p m a r o r r ea ) a e ( v t j 5 2 = o c0 0 7 t n e r r u c y l p p u s t n e c s e i u qi q g n i h c t i w s t o n5 1 10 4 1a y c n e u q e r f g n i h c t i w sf c s o t n e r r u c r o t c u d n i s u o u n i t n o c v 2 . 1 v n i v 5 . 2 0 2 40 0 60 8 7z h k t n e r r u c n w o d t u h si ) n d h s ( q v n e v 0 =6 30 5a r o t i n o m y r e t t a b w o l d l o h s e r h t e g a t l o v t u p n i y r e t t a b w o lv i b l t j 5 2 = o c0 9 10 0 20 1 2v m t n e r r u c t u p n i i b li i b l v i b l v m 0 0 2 =5 2 -0 5 -a n t u p t u o y r e t t a b w o lv ) l ( o b l i o b l 0 1 = m a0 5 1v m n i a g r o t c e t e d y r e t t a b w o la ) b l ( v m 1 w v ( d a o l n i t ; ) o b l o t j 5 2 = o c0 0 0 1 s t u p n i c i g o l e g a t l o v t u p n i e l b a n e v ) h ( n e v n i v 5 . 2 = 0 8 . 0v v ) l ( n e 0 2 . 0v note: (1) this device is esd sensitive. use of standard esd handling precautions is required. electrical characteristics
4 ? 2001 semtech corp. www.semtech.com power management sc1418 preliminary block diagram 200mv comp 400mv 750mv + - en gate drive and control logic ilimit comparator a=3 + - pwm comp. vout vin gnd + - current amp lbo + - lx lbi + - vref 1.24v error amp pin configuration ordering information pin descriptions notes: (1) only available in tape and reel packaging. a reel contains 2500 devices. s r e b m u n t r a pe g a k c a p r t s m i 8 1 4 1 c s ) 1 ( 8 - p o s m 1 2 3 4 lx vout top view (msop-8) 5 6 7 8 en gnd lbi lbo vin comp # n i pe m a n n i pn o i t c n u f n i p 1t u o v. e g a t l o v t u p t u o 2d n gd n u o r g 3o b l. t u p t u o r o t i n o m y r e t t a b w o l 4p m o c. r e i f i l p m a r o r r e f o t u p t u o . n i p n o i t a s n e p m o c 5n i v. n i p y l p p u s y r e t t a b 6i b l. t u p n i r o t i n o m y r e t t a b w o l 7n e l l i w w o l n i p s i h t g n i l l u p . n o i t r e s n i y r e t t a b n o p u t r a t s r o f d e r i w d r a h e b n a c . n i p e l b a n e . t r a p e h t n w o d t u h s 8x l. e r e h s t c e n n o c r o t c u d n i t u p n i , e d o n e s a h p
5 ? 2001 semtech corp. www.semtech.com power management sc1418 preliminary 2.0v 2.5v vin=3.0v 1.5v 60% 70% 80% 90% 100% 0.05 0.10 0.15 0.20 0.25 io (a) efficiency (%) sc1418 typical efficiency vs. io and v in 0 2 4 6 8 10 1.0 1.5 2.0 2.5 3.0 vin (v) d vo (mv) sc1418 typical line regulation -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0 50 100 150 200 250 300 io (ma) d vo (mv) sc1418 typical load regulation typical characteristics
6 ? 2001 semtech corp. www.semtech.com power management sc1418 preliminary
7 ? 2001 semtech corp. www.semtech.com power management sc1418 preliminary semtech corporation power management products division 652 mitchell rd., newbury park, ca 91320 phone: (805)498-2111 fax (805)498-3804 outline drawing - msop-8 contact information land pattern - msop-8
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