???? w w w . b e l l i n g . c o m . c n 1 BL8542B rev1.2, dec 2010 0.85v startup, 1mhz, 300ma iout, synchronous boost convert er d e s c r i p t i o n t h e b l 8 5 4 2 b i s a s t e p - u p c o n v e r t e r t h a t p r o v i d e s a b o o s t e d o u t p u t v o l t a g e f r o m a l o w v o l t a g e s o u r c e . b e c a u s e o f i t s p r o p r i e t a r y d e s i g n , i t s t a r t s u p a t a v e r y l o w i n p u t v o l t a g e d o w n t o 8 5 0 m v , m a k i n g i t a n i d e a l c h o i c e f o r s i n g l e c e l l a l k a l i n e / n i m h b a t t e r y o p e r a t i o n s . a s w i t c h i n g f r e q u e n c y o f 1 m h z m i n i m i z e s s o l u t i o n f o o t p r i n t b y a l l o w i n g t h e u s e o f t i n y , l o w p r o f i l e i n d u c t o r s a n d c e r a m i c c a p a c i t o r s . t h e c u r r e n t m o d e p w m d e s i g n i s i n t e r n a l l y c o m p e n s a t e d , r e d u c i n g e x t e r n a l p a r t s c o u n t . b l 8 5 4 2 b i s h o u s e d i n a t i n y s o t 2 3 - 5 a n d s o t 8 9 - 3 p a c k a g e . f e a t u r e s u p t o 9 5 % e f ? c i e n c y ? o u t p u t v o l t a g e a c c u r a c y 3 ? 1 m h z s w i tc h i n g f re q u e n c y a l l o w s s m a l l i n d u c t o r ? a n d o u t p u t c a p i n p u t b o o s t - s t r a p p i n g a l l o w s u s i n g s m a l l o r n o ? i n p u t c a p l o w v i n s t a r t - u p v o l t a g e d o w n t o 8 5 0 m v i d e a l ? f o r s i n g l e a l k a l i n e c e l l o p e r a t i o n s m a x i m u m o u t p u t c u r r e n t u p t o 3 0 0 m a ? l o w n o i s e p w m c o n t r o l ? i n t e r n a l l y c o m p e n s a t e d c u r r e n t m o d e c o n t r o l ? i n t e r n a l s y n c h r o n o u s r e c t i ? e r ? l o g i c c o n t r o l s h u t d o w n ( i q < 1 u a ) ? a p p l i c a t i o n s o n e t o t h r e e c e l l b a t t e r y o p e r a t e d d e v i c e s ? m e d i c a l i n s t r u m e n t s ? b l u e t o o t h h e a d s e t s ? f l a s h - b a s e d m p 3 p l a y e r s ? n o i s e c a n c e l i n g h e a d p h o n e s ? t y p i c a l a p p l i c a t i o n c i rc u i t n o t e : i n p u t c a p a c i t o r ( c i n = 0 . 4 7 u f ) a n d o u t p u t c a p a c i t o r ( c o u t 4 . 7 u f ) a r e r e c o m m e n d e d i n a l l a p p l i c a t i o n c i r c u i t . p i n c o n f i g u r a t i o n o r d e r i n g i n f o r m a t i o n pr oduct pr oduct code p ackage devices per r eel t op marking BL8542B- adj BL8542Bcb5tr sot23-5 3000 aaxz BL8542B- 3.3v BL8542Bcb5tr33 sot23-5 3000 aawz BL8542B- 5.0v BL8542Bcb5tr50 sot23-5 3000 aavz BL8542B-3.3v BL8542Bcc3tr33 sot89-3 1000 aawz xxxx BL8542B-5.0v BL8542Bcc3tr50 sot89-3 1000 aavz xxxx 2 3 1 sw g out BL8542B BL8542B BL8542B BL8542B sot23-5 sot89-3 x x x x : t h e l a s t 4 c h a r a c t e r s o f t h e l o t n o .
???? w w w . b e l l i n g . c o m . c n 2 BL8542B b l o c k d i ag r a m + - reference low input startup logic driver + - com par ator osc + - gm en fb g sw out d e t a i l d e s c r i p t i o n b l 8 5 4 2 b i s a l o w i n p u t v o l t a g e s t a r t u p , c u r r e n t m o d e d c - d c s t e p u p c o n v e r t e r . i t s o p e r a t i o n c a n b e b e s t u n d e r s t o o d b y r e f e r r i n g t o t h e b l o c k d i a g r a m . u p o n s t a r t i n g u p , t h e l o w v o l t a g e s t a r t u p c i r c u i t r y d r i v e s s w w i t h o n - o f f c y c l e s , t r a n s f e r r i n g e n e r g y f r o m i n p u t t o o u t b y s t o r i n g e n e r g y i n t h e i n d u c t o r d u r i n g o n - t i m e a n d r e l e a s i n g i t t o t h e o u t p u t d u r i n g o f f - t i m e . w h e n o u t r e a c h e s 2 v , t h e s t a r t u p c i r c u i t t u r n s o f f a n d t h e m a i n c o n t r o l l e r t a k e s o v e r . t h e m a i n c o n t r o l l o o p c o n s i s t s o f a r e f e r e n c e , a g m e r r o r a m p l i f i e r , a p w m c o n t r o l l e r , a c u r r e n t s e n s e a m p l i f i e r , a n o s c i l l a t o r , a p w m l o g i c c o n t r o l , a n d i t i s p o w e r s t a g e i n c l u d i n g i t s d r i v e r . t h e m a i n c o n t r o l l o o p i s a c l a s s i c c u r r e n t m o d e c o n t r o l l o o p . t h e g m s t a g e i n t e g r a t e s t h e e r r o r b e t w e e n f b a n d r e f , a n d i t s o u t p u t i s u s e d t o c o m p a r e w i t h a t r i a n g u l a r w a v e w h i c h t h e s u m m i n g re s u l t o f t h e c u r re n t s e n s e a m p l i f i e r o u t p u t a n d a s l o p e c o m p e n s a t i o n v o l t a g e . t h e o u t p u t o f t h e c o m p a r a t o r i s u s e d t o d r i v e t h e p o w e r s t a g e t o r e a c h r e g u l a t i o n . a p p l i c a t i o n i n f o r m a t i o n output voltage selecton t h e o u t p u t v o l t a g e s c a n b e s e t b y c o n n e c t i n g f b t o o u t , t o g o r t o t h e m i d p o i n t o f a r e s i s t o r d i v i d e r c o n n e c t e d t o o u t . s e e b e l o w t a b l e f o r d e t a i l s . f b = g v o u t = 5 . 0 v f b = o u t v o u t = 3 . 3 v f b t o r e s i s t o r d i v i d e r v o u t = 0 . 6 v ( 1 + r 1 / r 2 ) inductor selecton w i t h s w i t c h i n g f r e q u e n c y u p t o 1 m h z , s m a l l s u r f a c e m o u n t i n d u c t o r s c a n b e u s e d w i t h v a l u e s f r o m 2 . 2 u h t o 4 . 7 u h . f o r a g i v e n c h o s e n i n d u c t o r v a l u e a n d a p p l i c a t i o n c o n d i t i o n s m a k e s u r e t h e p e a k i n d u c t o r c u r r e n t d o e s n o t e x c e e d t h e m a x i m u m c u r r e n t r a t i n g o f t h e s e l e c t e d v e n d o r ' s i n d u c t o r . input and output capacitor selecton t h e b l 8 5 4 2 b ' s b o o t s t r a p a r c h i t e c t u r e a l l o w s t h e u s e o f v e r y s m a l l i n p u t c a p a c i t o r . f o r a p p l i c a t i o n s t h a t o n l y n e e d t o d r i v e s m a l l o u t p u t l o a d c u r r e n t , t h e i n p u t c a p a c i t o r i s o p t i o n a l , b e c a u s e o n c e o u t p u t i s s t a r t e d u p , t h e i c ' s i s p o w e r e d b y o u t , a q u i e t p o w e r s u p p l y . t h e o u t p u t c a p a c i t o r i s u s e d t o s t a b i l i z e t h e l o o p a n d p r o v i d e a c c u r r e n t t o t h e l o a d . a l o w e s r c e r a m i c c a p w i t h v a l u e s f r o m 2 . 2 u f t o 2 2 u f c a n b e u s e d . s m a l l e r v a l u e c a p a c i t o r s a r e g e n e r a l l y c h e a p e r w i t h s m a l l f o o t p r i n t s , w h i l e l a r g e r c a p a c i t o r p r o v i d e s l o w e r r i p p l e s a n d b e t t e r t r a n s i e n t l o a d r e s p o n s e s . a l s o , w h e n e x t r e m e l o w s t a r t u p v o l t a g e i s n e e d e d , l a r g e r o u t p u t c a p a c i t o r s a r e n e e d e d f o r t h e p a r t t o s t a r t u p u n d e r h e a v y l o a d c o n d i t i o n .
???? w w w . b e l l i n g . c o m . c n 3 BL8542B a b s o l u t e m a x i m u m r a t i n g p aramet er s v alue sw v oltage -0.3 ~ 6 v en, fb, out v oltage -0.3 ~ 6 v juntion t o ambient ther mal r esistance 190 o c/w maximum p ow er dissip ation 0.45 w operating t emperatur e range -40 ~ 150 o c s t orage t emperatur e -55 ~ 150 o c ir r e?ow lead t emperatur e and time 260 o c , 10s n o t e : e x c e e d t h e s e l i m i t s t o d a m a g e t o t h e d e v i c e . e x p o s u r e t o a b s o l u t e m a x i m u m r a t i n g c o n d i t i o n s m a y a f f e c t d e v i c e r e l i a b i l i t y . e l e c t r i c a l c h a r a c t e r i s t i c s t e s t c o n d i t i o n : v i n = 1 . 8 v , v o u t = 3 . 3 v , t a = 2 5 o c , u n l e s s o t h e r w i s e s p e c i ? e d . p aramet er s condition min. t yp. max. unit minimum input v oltage 0.7 v s tar tup v oltage 0.85 1.1 v dr opout v oltage, v out2.8v fb=out 3.3 v fb=g 5 v fb feedb ack v oltage v out=2.5 t o 5v 0.6 v fb input curr ent 50 na output v oltage range ext er nal divider 2.5 5 v quiescent curr ent at out vf b=0.7v 25 ua shut down supply curr ent at out en=g 0.1 1 ua nmos s wit ch on r esistance isw=100ma 0.3 ohm pmos s wit ch on r esistance isw=100ma 0.7 ohm nmos s wit ch curr ent limit 1 a sw leakage curr ent v out=5.5v , v sw=0 or 5.5v , en=g 1 ua en input curr ent 1 ua en input v oltage for low 0.3 v en input v oltage for high 0.6 v
???? w w w . b e l l i n g . c o m . c n 4 BL8542B t y p i c a l p e r f o r m a n c e c h a r a c t e r i s t i c s t y p i c a l v a l u e s a r e t e s t e d a t t a = 2 5 o c , u n l e s s o t h e r w i s e s p e c i ? e d . efficiency vs. output current ( vout = 3 . 3 v ; ta = 25 ) 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) vin=1.2v vin=1.8v vin=2.4v efficiency vs. output current ( vout = 5 v ; ta = 25 ) 20 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) vin=1.2v vin=1.8v vin=2.4v output voltage vs. output current ( vout = 3 . 3 v ; ta = 25 ) 3 3.05 3.1 3.15 3.2 3.25 0 50 100 150 200 250 300 350 400 450 output current(ma) output voltage(v) vin=1.2v vin=1.8v vin=2.4v minimum start-up voltage vs. output current (vout=3.3vta=25) 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 20 40 60 80 100 120 140 160 output current(ma) start-up voltage(v) maximum output current vs. input voltage ( l = 4 . 7 uh ta = 25 ) 0 100 200 300 400 500 600 700 0.5 1 1.5 2 2.5 3 3.5 4 input voltage(v) maximum output current(ma) vout=5v vout=3.3v no load input current vs. inpout voltage ( vout = 3 . 3 v ta = 25 no load ) 0 50 100 150 200 250 300 350 400 1.5 1.8 2.1 2.4 2.7 3 input voltage(v) input current(ua)
???? w w w . b e l l i n g . c o m . c n 5 BL8542B t y p i c a l p e r f o r m a n c e c h a r a c t e r i s t i c s t y p i c a l v a l u e s a r e t e s t e d a t t a = 2 5 o c , u n l e s s o t h e r w i s e s p e c i ? e d . vref ( t )/ vref ( t = 20 ) vs . temperature 0.97 0.974 0.978 0.982 0.986 0.99 0.994 0.998 1.002 1.006 1.01 -45 -25 -5 15 35 55 75 95 temerature ( ) normalized vref output voltage vs. temerature 3.17 3.18 3.19 3.2 3.21 3.22 3.23 3.24 3.25 -45 -25 -5 15 35 55 75 95 temerature ( ) output voltage(v) frequency vs. temperature 600 700 800 900 1000 1100 -45 -25 -5 15 35 55 75 95 temperature ( ) frequency(khz)
???? w w w . b e l l i n g . c o m . c n 6 BL8542B p a c k ag e o u t l i n e d i m e n s i o n p ackage so t23-5 devices per r eel 3000 dimension (mm) p ackage so t89-3 devices per r eel 1000 dimension (mm)
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