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c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 a n p e c r e s e r v e s t h e r i g h t t o m a k e c h a n g e s t o i m p r o v e r e l i a b i l i t y o r m a n u f a c t u r a b i l i t y w i t h o u t n o t i c e , a n d a d v i s e c u s t o m e r s t o o b t a i n t h e l a t e s t v e r s i o n o f r e l e v a n t i n f o r m a t i o n t o v e r i f y b e f o r e p l a c i n g o r d e r s . 2 a 2 4 v 3 4 0 k h z s y n c h r o n o u s b u c k c o n v e r t e r f e a t u r e s g e n e r a l d e s c r i p t i o n wide input voltage from 4.5v to 24v 2a continuous output current adjustable output voltage from 0.92v to 20v intergrated n-mosfet fixed 340khz switching frequency stable with low esr capacitors power-on-reset detection programmable soft-start over-temperature protection over-voltage protection current-limit protection with frequency foldback enable/shutdown function small sop-8 package lead free and green devices available (rohs compliant) a p p l i c a t i o n s lcd monitor/tv set-top box dsl, switch hub notebook computer APW7302 is a 2a synchronous buck converter with inte- grated power mosfets. the APW7302 design with a current-mode control scheme, can convert wide input voltage of 4.5v to 24v to the output voltage adjustable from 0.92v to 20v to provide excellent output voltage regulation. the APW7302 is also equipped with power-on-reset, soft- start, and whole protections (over-temperature, and cur- rent-limit) into a single package. this device, available sop-8, provides a very compact system solution external components and pcb area. s i m p l i f i e d 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 bs vin lx gnd 1 2 3 4 ss en comp fb 8 7 6 5 APW7302 sop-8 (top view) v out APW7302 v in
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 2 o r d e r i n g a n d m a r k i n g i n f o r m a t i o n n o t e : a n p e c l e a d - f r e e p r o d u c t s c o n t a i n m o l d i n g c o m p o u n d s / d i e a t t a c h m a t e r i a l s a n d 1 0 0 % m a t t e t i n p l a t e t e r m i n a t i o n f i n i s h ; w h i c h a r e f u l l y c o m p l i a n t w i t h r o h s . a n p e c l e a d - f r e e p r o d u c t s m e e t o r e x c e e d t h e l e a d - f r e e r e q u i r e m e n t s o f i p c / j e d e c j - s t d - 0 2 0 d f o r m s l c l a s s i f i c a t i o n a t l e a d - f r e e p e a k r e f l o w t e m p e r a t u r e . a n p e c d e f i n e s ? g r e e n ? t o m e a n l e a d - f r e e ( r o h s c o m p l i a n t ) a n d h a l o g e n f r e e ( b r o r c l d o e s n o t e x c e e d 9 0 0 p p m b y w e i g h t i n h o m o g e n e o u s m a t e r i a l a n d t o t a l o f b r a n d c l d o e s n o t e x c e e d 1 5 0 0 p p m b y w e i g h t ) . a b s o l u t e m a x i m u m r a t i n g s ( n o t e 1 ) symbol parameter rating unit v in vin supply voltage (vin to gnd) - 0.3 ~ 30 v v lx lx to gnd voltage - 1 ~v in +0.3 v en, fb, comp , ss to gnd voltage - 0.3 ~ 6 v v bs bs to gnd voltage v lx - 0.3 ~ v lx +6 v p d power dissipation internally limited w t j junction temperature 150 o c t stg storage temperature - 65 ~ 150 o c t sdr maximum lead soldering temperature , 10 seconds 26 0 o c note1: stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. these are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under "recom- mended operating conditions" is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability t h e r m a l c h a r a c t e r i s t i c s symbol parameter typical value unit q ja junction - to - ambient resistance in f ree a ir (note 2) sop - 8 110 o c/w q jc junction - to - case resistance in f ree a ir sop - 8 30 o c/w note 2: q ja is measured with the component mounted on a high effective thermal conductivity test board in free air. symbol parameter range unit v in vin supply voltage 4.5 ~ 24 v v out converter output voltage 0.92 ~ 20 v i out converter output current 0 ~ 2 a r e c o m m e n d e d o p e r a t i n g c o n d i t i o n s ( n o t e 3 ) apw 7302 handling code tem perature range package code apw 7302 xxxxx package code k : sop-8 temperature range i : -40 to 85 o c handling code tr : tape & reel assembly material g : halogen and lead free device apw 7302 k : assembly material xxxxx - date code
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 3 symbol parameter range unit t a ambient temperature - 40 ~ 85 o c t j junction temperature - 40 ~ 125 o c r e c o m m e n d e d o p e r a t i n g c o n d i t i o n s ( c o n t . ) ( n o t e 3 ) note 3: refer to the typical application circuit. 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 APW7302 symbol parameter test conditions min. typ. max. unit supply current i vin vin supply current v fb =1v, v en =3v, lx=nc - 1.9 - ma i vin_sd vin shutdown supply current v en =0v - 20 - m a power - on - r eset (por) vin por voltage threshold v in rising 3 .9 4.1 4.3 v vin por hysteresis - 0.5 - v reference voltage v ref reference voltage regulated on fb pin 0.9 0.92 0.94 v oscillator and duty cycle f osc oscillator frequency 310 340 370 khz foldback frequency v fb =0v - 110 - khz maximum converter ? s duty - 90 - % minimum on time (note 4) - 220 - ns power mosfet high/low side mosfet on resistance i out =2a - 130 - m w high / low side mosfet leakage current v en =0v - - 10 m a current - mode pwm converter g m error amplifier transconductance - 800 - m a/v error amplifier voltage gain comp=nc (note 4) - 400 - v/v switch current to comp voltage transconductance - 4.5 - a/v protecti ons i lim high side mosfet current - limit peak current - 3.5 - a low side mosfet current - limit from drain to source - 1 - a t otp over - temperature trip point (note 4) - 160 - c over - temperature hysteresis (note 4) - 50 - c over - volta ge protection (note 4) - 120 - % unless otherwise specified, these specifications apply over v in =12v, v out = 3.3v, v en =3v and t a =25 o c.
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 4 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 ( c o n t . ) APW7302 symbol parameter test conditions min. typ. max. unit soft - start, enable and input currents i ss soft - start current - 6 - m a en enable threshold voltage v in =4.5~24v 0.4 - 2 v en under - voltage lockout (uvlo) threshold v en rising 2.3 2.5 2. 7 v en uvlo hysteresis - 200 - mv n ote 4 : gu a rantee by design . unless otherwise specified, these specifications apply over v in =12v, v out = 3.3v, v en =3v and t a =25 o c.
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 5 t y p i c a l o p e r a t i n g c h a r a c t e r i s t i c s r e f e r e n c e v o l t a g e , v r e f ( v ) reference voltage vs. junction temperature junction temperature, t j ( o c ) 0.9 0.905 0.91 0.915 0.92 0.925 0.93 0.935 0.94 -50 -25 0 25 50 75 100 125 150 oscillator frequency vs. junction temperature junction temperature, t j ( x c ) 300 310 320 330 340 350 360 -50 -25 0 25 50 75 100 125 150 o s c i l l a t o r f r e q u e n c y v i n i n p u t c u r r e n t , i v i n ( m a ) vin supply voltage , v in (v) 1 1.2 1.4 1.6 1.8 2 0 4 8 12 16 20 24 vin input current vs. supply voltage refer to the ?typical application circuit? the test conditions are v in =12v, v out =3.3v, l1=10 m h, c2=22 m f, t a = 25 o c unless otherwise specified. output current , i out ( a ) e f f i c i e n c y ( % ) output current vs . efficiency 50 . 00 % 55 . 00 % 60 . 00 % 65 . 00 % 70 . 00 % 75 . 00 % 80 . 00 % 85 . 00 % 90 . 00 % 95 . 00 % 100 . 00 % 0 0 . 25 0 . 5 0 . 75 1 1 . 25 1 . 5 1 . 75 2 v in = 12 v v out = 5 v v out = 3 . 3 v v out = 2 . 5 v
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 6 o p e r a t i n g w a v e f o r m s power off ch1: v in , 5v/div, dc ch2: v out , 2v/div, dc time: 5m s/div 2 1 3 ch3: i l1 , 2a/div, dc v in v out i l1 i out =2a time: 50 m s/div load transient response 1 2 ch1: v out , 200mv/div, offset=3.3v ch2: i l1 , 1a/div, dc i out =0.5a-2a-0.5a, rise/fall time=10 m s i out v out refer to the ?typical application circuit? the test conditions are v in =12v, v out =3.3v, l1=10 m h, c2=22 m f, t a = 25 o c unless otherwise specified. power on ch 1 : v in , 5 v / div , dc ch 2 : v out , 2 v / div , dc time : 5 m s / div 2 1 3 ch 3 : i l 1 , 2 a / div , dc i out = 5 a v in v out i l 1 i out = 2 a load transient response 1 2 ch 1 : v out , 200 mv / div , offset = 3 . 3 v ch 2 : i l 1 , 1 a / div , dc time : 50 m s / div i out v out i out = 0 a - 2 a - 0 a , rise / fall time = 10 m s
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 7 switching waveform 1 2 ch1: v lx , 5v/div, dc ch2: i l1 , 0.5a/div, dc time: 1 m s/div v lx i l1 i out =0a switching waveform 1 2 ch1: v lx , 5v/div, dc ch2: i l1 , 2a/div, dc time: 1 m s/div i out =2a v lx i l1 short circuit ch1: v out , 1v/div, dc ch2: i l1 , 2a/div, dc time: 1 s/div 1 2 3 v out is shorted to gnd by a short wire v out i l1 o p e r a t i n g w a v e f o r m s ( c o n t . ) refer to the ?typical application circuit? the test conditions are v in =12v, v out =3.3v, l1=10 m h, c2=22 m f, t a = 25 o c unless otherwise specified. 1 2 ch 1 : v out , 1 v / div , dc time : 50 m s / div ch 2 : i l 1 , 2 a / div , dc v out i l 1 i out = 0 ~ 4 a over current
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 8 line transient response v out ch1: v in , 5v/div, dc time: 50 m s/div 2 1 ch2: v out , 50mv/div, offset=3.3v v in =12 to 20v, rise/fall time=10 m s v in v out o p e r a t i n g w a v e f o r m s ( c o n t . ) refer to the ?typical application circuit? the test conditions are v in =12v, v out =3.3v, l1=10 m h, c2=22 m f, t a = 25 o c unless otherwise specified.
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 9 p i n d e s c r i p t i o n pin no. name function 1 bs high - side gate drive boost input. bs supplies the voltage to drive the high - side n - channel mosfet. at least 10nf capacitor should be connected from lx to bs to supply the high side switch. 2 vin power input. vin supplies the power (4. 5 v to 24 v) to the control circuitry, gate drivers and step - down converter switches. connecting a ceramic bypass capacitor and a suitably large capacitor between vin and gnd eliminates switching noise and voltage ripple on the input to the ic. 3 l x power switching output. lx is the drain of the n - channel power mosfet to supply power to the output lc filter. 4 gnd ground. connect the exposed pad on backside to pin 4. 5 fb output feedback input. the apw7 302 senses the feedback voltage via fb and re gulates the voltage at 0. 92 v. connecting fb with a resistor - divider from the converter?s output sets the output voltage from 0. 92 v to 20v . 6 comp output of the error amplifier. connect a series rc network from comp to gnd to compensate the regulation cont rol loop. in some cases, an additional capacitor from comp to gnd is required. 7 en enable input. en is a digital input that turns the regulator on or off. pull up with 100k w resistor for automatic startup. 8 ss soft - start control input. ss controls the soft - start period. connect a capacitor from ss to gnd to set the soft - start period. a 0.1 m f capacitor sets the soft - start period to 1 5 ms. to disable the soft - start feature, leave ss unconnected. b l o c k d i a g r a m lx gate control v ref fault logics error amplifier fb inhibit gnd por power - on - reset 5 v uvlo current sense amplifier en comp oscillator 340 khz / 1 10 khz slope compensation current comparator 1 . 5 v over temperature protection current - limit gate driver gate driver gm vin 2 . 5 / 2 . 3 v 1 bs 3 4 2 5 6 7 8 ss 5 v vin internal regulator 5 v fb 0 . 6 v enable 120 % v ref ovp 6 m a 5 v otp current sense amplifier loc loc
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 0 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 r e c o m m e n d e d f e e d b a c k c o m p e n s a t i o n v a l u e vin(v) v out (v) l1( m h) c2( m f) r1(k w ) r2(k w ) r3(k w ) c5(nf) 24 5 10 22(ceremic) 39 9.1 6.8 3.9 12 5 10 44 (ceremic) 39 9.1 5 1.5 12 3.3 10 22 (ceremic) 24 9.1 6.8 3.9 12 2.5 10 22 (ceremic) 15 9.1 6.8 3.9 APW7302 vin 2 7 en comp 6 gnd 4 lx 3 fb 5 bs 1 ss 8 v in 4.5v~24v v out 3.3v/2a c1 10 m f c2 22 m f r1 24k r2 9.1k l1 10 m f c4 0.1 m f c3 10n f c5 3.9n f r3 6.8k r4 100k
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 1 f u n c t i o n d e s c r i p t i o n m a i n c o n t r o l l o o p t h e a p w 7 3 0 2 i s a c o n s t a n t f r e q u e n c y c u r r e n t m o d e s w i t c h i n g r e g u l a t o r . d u r i n g n o r m a l o p e r a t i o n , t h e i n t e r - n a l n - c h a n n e l p o w e r m o s f e t i s t u r n e d o n e a c h c y c l e w h e n t h e o s c i l l a t o r s e t s a n i n t e r n a l r s l a t c h a n d w o u l d b e t u r n e d o f f w h e n a n i n t e r n a l c u r r e n t c o m p a r a t o r ( i c m p ) r e s e t s t h e l a t c h . t h e p e a k i n d u c t o r c u r r e n t a t w h i c h i c m p r e s e t s t h e r s l a t c h i s c o n t r o l l e d b y t h e v o l t a g e o n t h e c o m p p i n , w h i c h i s t h e o u t p u t o f t h e e r r o r a m p l i f i e r ( e a m p ) . a n e x t e r n a l r e s i s t i v e d i v i d e r c o n n e c t e d b e t w e e n v o u t a n d g r o u n d a l l o w s t h e e a m p t o r e c e i v e a n o u t p u t f e e d b a c k v o l t a g e v f b a t f b p i n . w h e n t h e l o a d c u r r e n t i n c r e a s e s , i t c a u s e s a s l i g h t d e c r e a s e i n v f b r e l a t i v e t o t h e 0 . 9 2 v r e f e r e n c e , w h i c h i n t u r n c a u s e s t h e c o m p v o l t - a g e t o i n c r e a s e u n t i l t h e a v e r a g e i n d u c t o r c u r r e n t m a t c h e s t h e n e w l o a d c u r r e n t . vin power-on-reset (por) and en under-voltage lockout the APW7302 keep monitoring the voltage on vin pin to prevent wrong logic operations which may occur when vin voltage is not high enough for the internal control circuitry to operate. the vin por has a rising threshold of 4.1v (typical) with 0.5v of hysteresis. an external under-voltage lockout (uvlo) is sensed at the en pin. the en uvlo has a rising threshold of 2.5v with 0.2v of hysteresis. the en pin should be connected a resistor divider from vin to en. after the vin and en voltages exceed their respective voltage thresholds, the ic starts a start-up process and then ramps up the output voltage to the setting of output voltage. over-temperature protection (otp) the over-temperature circuit limits the junction tempera- ture of the APW7302. when the junction temperature ex- ceeds t j = +160 o c, a thermal sensor turns off the power mosfet, allowing the devices to cool. the thermal sen- sor allows the converter to start a start-up process and regulate the output voltage again after the junction tem- perature cools by 50 o c. the otp is designed with a 50 o c hysteresis to lower the average t j during continuous thermal overload conditions, increasing lifetime of the lc. c u r r e n t - l i m i t p r o t e c t i o n t h e a p w 7 3 0 2 m o n i t o r s t h e o u t p u t c u r r e n t , f l o w i n g t h r o u g h t h e n - c h a n n e l p o w e r m o s f e t , a n d l i m i t s t h e i c f r o m d a m a g e s d u r i n g o v e r l o a d , s h o r t - c i r c u i t a n d o v e r - v o l t a g e c o n d i t i o n s . f r e q u e n c y f o l d b a c k t h e f o l d b a c k f r e q u e n c y i s c o n t r o l l e d b y t h e f b v o l t a g e . w h e n t h e f b p i n v o l t a g e i s u n d e r 0 . 6 v , t h e f r e q u e n c y o f t h e o s c i l l a t o r w i l l b e r e d u c e d t o 1 1 0 k h z . t h i s l o w e r f r e - q u e n c y a l l o w s t h e i n d u c t o r c u r r e n t t o s a f e l y d i s c h a r g e , t h e r e b y p r e v e n t i n g c u r r e n t r u n a w a y . t h e o s c i l l a t o r ? s f r e - q u e n c y w i l l s w i t c h t o i t s d e s i g n e d r a t e w h e n t h e f e e d b a c k v o l t a g e o n f b r i s e s a b o v e t h e r i s i n g f r e q u e n c y f o l d b a c k t h r e s h o l d ( 0 . 6 v , t y p i c a l ) a g a i n . o v e r - v o l t a g e p r o t e c t i o n t h e o v e r - v o l t a g e f u n c t i o n m o n i t o r s t h e o u t p u t v o l t a g e b y f b p i n . w h e n t h e f b v o l t a g e i n c r e a s e o v e r 1 2 0 % o f t h e r e f e r e n c e v o l t a g e , t h e o v e r - v o l t a g e p r o t e c t i o n c o m p a r a - t o r w i l l f o r c e t h e l o w - s i d e m o s f e t g a t e d r i v e r h i g h . t h i s a c t i o n a c t i v e l y p u l l s d o w n t h e o u t p u t v o l t a g e . a s s o o n a s t h e o u t p u t v o l t a g e i s w i t h i n r e g u l a t i o n , t h e o v p c o m p a r a - t o r i s d i s e n g a g e d . t h e c h i p w i l l r e s t o r e i t s n o r m a l o p e r a t i o n . e n a b l e / s h u t d o w n d r i v i n g e n t o g r o u n d p l a c e s t h e a p w 7 3 0 2 i n s h u t d o w n . w h e n i n s h u t d o w n , t h e i n t e r n a l p o w e r m o s f e t t u r n s o f f , a l l i n t e r n a l c i r c u i t r y s h u t s d o w n .
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 2 a p p l i c a t i o n i n f o r m a t i o n s e t t i n g o u t p u t v o l t a g e i n d u c t o r c a p a c i t o r s e l e c t i o n w h e r e d i s t h e d u t y c y c l e o f t h e p o w e r m o s f e t . f o r a t h r o u g h h o l e d e s i g n , s e v e r a l e l e c t r o l y t i c c a p a c i t o r s m a y b e n e e d e d . f o r s u r f a c e m o u n t d e s i g n s , s o l i d t a n t a - l u m c a p a c i t o r s c a n b e u s e d , b u t c a u t i o n m u s t b e e x e r - c i s e d w i t h r e g a r d t o t h e c a p a c i t o r s u r g e c u r r e n t r a t i n g . ) a ( ) d 1 ( d i i out rms - = ) v ( esr i v out d = d out osc cout c f 8 i v d = d 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 i s d e t e r m i n e d b y : use small ceramic capacitors for high frequency decoupling and bulk capacitors to supply the surge cur- rent needed each time the n-channel power mosfet (q1) turns on. place the small ceramic capacitors physi- cally close to the vin and between the vin and gnd. the important parameters for the bulk input capacitor are the voltage rating and the rms current rating. for reliable operation, select the bulk capacitor with voltage and current ratings above the maximum input voltage and largest rms current required by the circuit. the capacitor voltage rating should be at least 1.25 times greater than the maximum input voltage and a voltage rating of 1.5 times is a conservative guideline. the rms current (irms) of the bulk input capacitor is calculated as the following equation: a n o u t p u t c a p a c i t o r i s r e q u i r e d t o f i l t e r t h e o u t p u t a n d s u p - p l y t h e l o a d t r a n s i e n t c u r r e n t . t h e f i l t e r i n g r e q u i r e m e n t s a r e t h e f u n c t i o n o f t h e s w i t c h i n g f r e q u e n c y a n d t h e r i p p l e c u r r e n t ( d i ) . t h e o u t p u t r i p p l e i s t h e s u m o f t h e v o l t a g e s , h a v i n g p h a s e s h i f t , a c r o s s t h e e s r a n d t h e i d e a l o u t p u t c a p a c i t o r . t h e p e a k - t o - p e a k v o l t a g e o f t h e e s r i s c a l c u - a t e d a s t h e f o l l o w i n g e q u a t i o n s : ) v ( ) r r 1 ( 92 . 0 vout 2 1 + = t o p r e v e n t s t r a y p i c k u p , p l e a s e l o c a t e r e s i s t o r s r 1 a n d r 2 c l o s e t o a p w 7 3 0 2 . esr i v l f ) d 1 ( v i v v d esr osc out in out d = - = d = t h e p e a k - t o - p e a k v o l t a g e o f t h e i d e a l o u t p u t c a p a c i t o r i s c a l c u l a t e d a s t h e f o l l o w i n g e q u a t i o n s : f o r t h e a p p l i c a t i o n s u s i n g b u l k c a p a c i t o r s , t h e d v c o u t i s m u c h s m a l l e r t h a n t h e v e s r a n d c a n b e i g n o r e d . t h e r e f o r e , t h e a c p e a k - t o - p e a k o u t p u t v o l t a g e ( d v o u t ) i s s h o w n b e l o w : o u t p u t c a p a c i t o r s e l e c t i o n f o r t h e a p p l i c a t i o n s u s i n g b u l k c a p a c i t o r s , t h e v e s r i s m u c h s m a l l e r t h a n t h e d v c o u t a n d c a n b e i g n o r e d . t h e r e f o r e , t h e a c p e a k - t o - p e a k o u t p u t v o l t a g e ( d v o u t ) i s t o d v c o u t . f i g u r e 1 . c o n v e r t e r w a v e f o r m s i out v lx t=1/f osc i l i q1 i cout i out i i dt v out v out . . . . . . . . . . . ( 1 ) . . . . . . . . . . . ( 2 ) . . . . . . . . . . . ( 3 ) . . . . . . . . . . . ( 4 ) . . . . . . . . . . . ( 5 ) v in v out c in c out l q1 lx esr i l i out i q1 i cout vin q2
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 3 a p p l i c a t i o n i n f o r m a t i o n ( c o n t . ) o u t p u t c a p a c i t o r s e l e c t i o n ( c o n t . ) t h e l o a d t r a n s i e n t r e q u i r e m e n t s a r e t h e f u n c t i o n o f t h e s l e w r a t e ( d i / d t ) a n d t h e m a g n i t u d e o f t h e t r a n s i e n t l o a d u r r e n t . t h e s e r e q u i r e m e n t s a r e g e n e r a l l y m e t w i t h a m i x o f c a p a c i t o r s a n d c a r e f u l l a y o u t . h i g h f r e q u e n c y c a - p a c i t o r s i n i t i a l l y s u p p l y t h e t r a n s i e n t a n d s l o w t h e c u r r e n t l o a d r a t e s e e n b y t h e b u l k c a p a c i t o r s . t h e b u l k f i l t e r c a - p a c i t o r v a l u e s a r e g e n e r a l l y d e t e r m i n e d b y t h e e s r ( e f f e c t i v e s e r i e s r e s i s t a n c e ) a n d v o l t a g e r a t i n g r e q u i r e - m e n t s r a t h e r t h a n a c t u a l c a p a c i t a n c e r e q u i r e m e n t s . h i g h f r e q u e n c y d e c o u p l i n g c a p a c i t o r s s h o u l d b e p l a c e d a s c l o s e t o t h e p o w e r p i n s o f t h e l o a d a s p h y s i c a l l y p o s s i b l e . b e c a r e f u l n o t t o a d d i n d u c t a n c e i n t h e c i r c u i t b o a r d w i r i n g t h a t c o u l d c a n c e l t h e u s e f u l n e s s o f t h e s e l o w i n d u c t a n c e c o m p o n e n t s . a n a l u m i n u m e l e c t r o l y t i c c a p a c i t o r ? s e s r v a l u e i s r e l a t e d t o t h e c a s e s i z e w i t h l o w e r e s r a v a i l a b l e i n l a r g e r c a s e s i z e s . h o w e v e r , t h e e q u i v a - l e n t s e r i e s i n d u c t a n c e ( e s l ) o f t h e s e c a p a c i t o r s i n c r e a s e s w i t h c a s e s i z e a n d c a n r e d u c e t h e u s e f u l n e s s o f t h e c a - p a c i t o r t o h i g h s l e w - r a t e t r a n s i e n t l o a d i n g . table1 capacitor selection guide vender model capacitance ( m f) tc voltage rating(v) si2e murata grm31cr61e106k 10 x5r 25 1206 murata grm31cr61c226k 22 x5r 16 1206 t h e o p e r a t i n g f r e q u e n c y a n d i n d u c t o r s e l e c t i o n a r e i n t e r - r e l a t e d i n t h a t h i g h e r o p e r a t i n g f r e q u e n c i e s p e r m i t t h e u s e o f a s m a l l e r i n d u c t o r f o r t h e s a m e a m o u n t o f i n d u c t o r r i p p l e c u r r e n t . h o w e v e r , t h i s i s a t t h e e x p e n s e o f e f f i c i e n c y d u e t o a n i n c r e a s e i n m o s f e t g a t e c h a r g e l o s s e s . t h e e q u a t i o n ( 2 ) s h o w s t h a t t h e i n d u c t a n c e v a l u e h a s a d i r e c t e f f e c t o n r i p p l e c u r r e n t . a c c e p t i n g l a r g e r v a l u e s o f r i p p l e c u r r e n t a l l o w s t h e u s e o f l o w i n d u c t a n c e s , b u t r e s u l t s i n h i g h e r o u t p u t v o l t a g e r i p p l e a n d g r e a t e r c o r e l o s s e s . a r e a s o n a b l e s t a r t i n g p o i n t f o r s e t t i n g r i p p l e c u r r e n t i s d i < 0 . 4 x i o u t ( m a x ) . p l e a s e b e n o - t i c e d t h a t t h e m a x i m u m r i p p l e c u r r e n t o c c u r s a t t h e m a x i - m u m i n p u t v o l t a g e . t h e m i n i m u m i n d u c t a n c e o f t h e i n - u c t o r i s c a l c u l a t e d b y u s i n g t h e f o l l o w i n g e q u a t i o n : i n d u c t o r v a l u e c a l c u l a t i o n w h e r e . . . . . . . . . . . ( 6 ) in(max) in v v = 1.2 v l 340000 ) v - (v v in out in out (h) v 408000 ) v - (v v l in out in out 3 table2 inductor selection guide vender model inductance ( m h) dcr (m w ) current rating(a) cyntec pcmb063t - 100ms 10 62 4 gausstek pl94p051m - 15u 15 50 3 gausstek pl94p051m - 10u 10 38 3.8
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 4 a p p l i c a t i o n i n f o r m a t i o n ( c o n t . ) t h e r m a l c o n s i d e r a t i o n l a y o u t c o n s i d e r a t i o n i n h i g h p o w e r s w i t c h i n g r e g u l a t o r , a c o r r e c t l a y o u t i s i m p o r t a n t t o e n s u r e p r o p e r o p e r a t i o n o f t h e r e g u l a t o r . i n g e n e r a l , i n t e r c o n n e c t i n g i m p e d a n c e s h o u l d b e m i n i m i z e d b y u s i n g s h o r t , w i d e p r i n t e d c i r c u i t t r a c e s . s i g n a l a n d p o w e r g r o u n d s a r e t o b e k e p t s e p a r a t i n g a n d f i n a l l y c o m b i n e d u s i n g t h e g r o u n d p l a n e c o n s t r u c t i o n o r s i n g l e p o i n t g r o u n d i n g . f i g u r e 3 i l l u s t r a t e s t h e l a y o u t , w i t h b o l d l i n e s i n d i c a t i n g h i g h c u r r e n t p a t h s . c o m p o n e n t s a l o n g t h e b o l d l i n e s s h o u l d b e p l a c e d c l o s e t o g e t h e r . b e l o w i s a c h e c k l i s t f o r y o u r l a y o u t : 1 . b e g i n t h e l a y o u t b y p l a c i n g t h e p o w e r c o m p o n e n t s f i r s t . o r i e n t t h e p o w e r c i r c u i t r y t o a c h i e v e a c l e a n p o w e r f l o w p a t h . i f p o s s i b l e , m a k e a l l t h e c o n n e c t i o n s o n o n e s i d e o f t h e p c b w i t h w i d e , c o p p e r f i l l e d a r e a s . 2 . i n f i g u r e 3 , t h e l o o p s w i t h s a m e c o l o r b o l d l i n e s c o n - d u c t h i g h s l e w r a t e c u r r e n t . t h e s e i n t e r c o n n e c t i n g i m - p e d a n c e s s h o u l d b e m i n i m i z e d b y u s i n g w i d e a n d s h o r t p r i n t e d c i r c u i t t r a c e s . 3 . k e e p t h e s e n s i t i v e s m a l l s i g n a l n o d e s ( f b , c o m p ) a w a y f r o m s w i t c h i n g n o d e s ( l x o r o t h e r s ) o n t h e p c b a n d i t s h o u l d b e p l a c e d n e a r t h e i c a s c l o s e a s p o s s i b l e . t h e r e f o r e , p l a c e t h e f e e d b a c k d i v i d e r a n d t h e f e e d b a c k c o m p e n s a t i o n n e t w o r k c l o s e t o t h e i c t o a v o i d s w i t c h i n g n o i s e . c o n n e c t t h e g r o u n d o f f e e d b a c k d i v i d e r d i r e c t l y t o t h e g n d p i n o f t h e i c u s i n g a d e d i c a t e d g r o u n d t r a c e . the APW7302 maximum power dissipation depends on the thermal resistance and temperature difference be- tween the die junction and ambient air. the power dissi- pation p d across the device is: p d = (t j - t a ) / q ja where (t j -t a ) is the temperature difference between the junction and ambient air. q ja is the thermal resistance between junction and ambient air. for normal operation, do not exceed the maximum junc- tion temperature rating of t j = 125 o c. the calculated power dissipation should less than: p d = (125-25)/110 = 0.90(w) 4 . p l a c e t h e d e c o u p l i n g c e r a m i c c a p a c i t o r c 1 n e a r t h e v i n a s c l o s e a s p o s s i b l e . u s e a w i d e p o w e r g r o u n d p l a n e t o c o n n e c t t h e c 1 , c 2 , a n d s c h o t t k y d i o d e t o p r o v i d e a l o w i m p e d a n c e p a t h b e t w e e n t h e c o m p o n e n t s f o r l a r g e a n d h i g h s l e w r a t e c u r r e n t . f i g u r e 2 . c u r r e n t p a t h d i a g r a m f i g u r e 3 . r e c o m m e n d e d l a y o u t d i a g r a m ambient temperature, t a ( o c ) m a x i m u m p o w e r d i s s i p a t i o n , p d ( w ) sop-8 0 25 50 75 100 125 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 3 2 1 sop-8 APW7302 5 6 7 8 4 l1 c2 c 1 v lx v in v out ground input capacitor c1 should be near the ic as close as possible sensitive node (fb, comp) should be away from switching node(lx) and it should be placed near the ic with short trace power path should be short and wide numerous vias connected from the thermal pad to the solderside ground plane(s) should be used to enhance heat dissipation lx en vin gnd comp u1 APW7302 fb l1 c2 load v out bs r1 r2 feedback divider c5 r3 compensation network v in c3 c 1 + + - -
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 5 p a c k a g e i n f o r m a t i o n s o p - 8 l view a 0 . 2 5 seating plane gauge plane note: 1. follow jedec ms-012 aa. 2. dimension ? d ? does not include mold flash, protrusions or gate burrs. mold flash, protrusion or gate burrs shall not exceed 6 mil per side. 3. dimension ? e ? does not include inter-lead flash or protrusions. inter-lead flash and protrusions shall not exceed 10 mil per side. s y m b o l min. max. 1.75 0.10 0.17 0.25 0.25 a a1 c d e e1 e h l millimeters b 0.31 0.51 sop-8 0.25 0.50 0.40 1.27 min. max. inches 0.069 0.004 0.012 0.020 0.007 0.010 0.010 0.020 0.016 0.050 0 0.010 1.27 bsc 0.050 bsc a2 1.25 0.049 0 8 0 8 3.80 5.80 4.80 4.00 6.20 5.00 0.189 0.197 0.228 0.244 0.150 0.157 d e e e 1 see view a c b h x 4 5 a 2 a aaa c nx aaa 0.10 0.004
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 6 application a h t1 c d d w e1 f 330.0 ? 2.00 50 min. 12.4+2.00 - 0.00 13.0+0.50 - 0.20 1.5 min. 20.2 min. 12.0 ? 0.30 1.75 ? 0.10 5.5 ? 0.05 p 0 p1 p 2 d 0 d1 t a 0 b 0 k 0 sop - 8 4.0 ? 0.10 8.0 ? 0.10 2.0 ? 0.05 1.5+0.10 - 0.00 1.5 min. 0.6+0.00 - 0.40 6.40 ? 0.20 5.20 ? 0.20 2.10 ? 0.20 (mm) d e v i c e s p e r u n i t c a r r i e r t a p e & r e e l d i m e n s i o n s package type unit quantity sop - 8 tape & reel 2500 a e 1 a b w f t p0 od0 b a0 p2 k0 b 0 section b-b section a-a od1 p1 h t1 a d
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 7 t a p i n g d i r e c t i o n i n f o r m a t i o n s o p - 8 c l a s s i f i c a t i o n p r o f i l e user direction of feed
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 8 c l a s s i f i c a t i o n r e f l o w p r o f i l e s profile feature sn - pb eutectic assembly pb - free assembly preheat & soak temperature min (t smin ) temperature max (t smax ) time (t smin to t smax ) ( t s ) 100 c 150 c 60 - 120 seconds 150 c 200 c 60 - 1 2 0 seconds average ramp - up rate (t smax to t p ) 3 c/second ma x. 3 c/second max. liquidous temperature ( t l ) time at l iquidous (t l ) 183 c 60 - 150 seconds 217 c 60 - 150 seconds peak package body temperature (t p ) * see classification temp in table 1 see classification temp in table 2 time (t p ) ** within 5 c of the spec ified c lassification t emperature ( t c ) 2 0 ** seconds 3 0 ** seconds average r amp - down rate (t p to t smax ) 6 c/second max. 6 c/second max. time 25 c to p eak t emperature 6 minutes max. 8 minutes max. * tolerance for peak profile temperature (t p ) is defined a s a supplier minimum and a user maximum. ** tolerance for time at peak profile temperature (t p ) is defined as a supplier minimum and a user maximum. table 2. pb - free process ? classification temperatures (tc) package thickness volume mm 3 <350 volume mm 3 350 - 2000 volume mm 3 >2000 <1.6 mm 260 c 260 c 260 c 1.6 mm ? 2.5 mm 260 c 250 c 245 c 3 2.5 mm 250 c 245 c 245 c table 1. snpb eutectic process ? classification temperatures (tc) package thickness volume mm 3 <350 volume mm 3 3 350 <2.5 mm 235 c 22 0 c 3 2.5 mm 220 c 220 c test item method description solderability jesd - 22, b102 5 sec, 245 c holt jesd - 22, a108 1000 hrs, bias @ t j =125 c pct jesd - 22, a102 168 hrs, 100 % rh, 2atm , 121 c tct jesd - 22, a104 500 cycles, - 65 c~150 c hbm mil - std - 883 - 3015.7 vhbm ? 1 kv mm jesd - 22, a1 15 vmm ? 100v latch - up jesd 78 10ms, 1 tr ? 100ma r e l i a b i l i t y t e s t p r o g r a m
c o p y r i g h t ? a n p e c e l e c t r o n i c s c o r p . r e v . a . 4 - n o v . , 2 0 1 1 a p w 7 3 0 2 w w w . a n p e c . c o m . t w 1 9 c u s t o m e r s e r v i c e a n p e c e l e c t r o n i c s c o r p . head office : no.6, dusing 1st road, sbip, hsin-chu, taiwan, r.o.c. tel : 886-3-5642000 fax : 886-3-5642050 t a i p e i b r a n c h : 2 f , n o . 1 1 , l a n e 2 1 8 , s e c 2 j h o n g s i n g r d . , s i n d i a n c i t y , t a i p e i c o u n t y 2 3 1 4 6 , t a i w a n t e l : 8 8 6 - 2 - 2 9 1 0 - 3 8 3 8 f a x : 8 8 6 - 2 - 2 9 1 7 - 3 8 3 8

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