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1/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct. 14 , 20 11 AX3513A 1.4m hz, 1 a synchronous step -down converter ? general description AX3513A is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. the device is available in an adjustable version . supply current with no load is 250 ua and drops to <1ua in shutdown. the 2.5v to 5.5v input voltage range makes AX3513A ideally suited for single li-ion, two to three aa battery-powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. pwm operation provides very low output ripple voltage for noise sensitive applications. switching frequency is internally set at 1.4mhz, allowing the use of small surface mount inductors and capacitors. the internal synchronous switch increases efficiency and decreases need of an external schottky diode. low output voltages are easily supported with the 0.6v feedback reference voltage. AX3513A is available in small tsot23- 5l and tdfn- 6l packages. ? features - 2.5v to 5.5v input voltage range - output voltage from 0.6v to vin - high efficiency: up to 96 % - 1.4mhz constant frequency operation - up to 1a output current - quiescent current: 250 ua ( typical ) - no schottky diode required - current mode operation for excellent line and load transient response - current limit, enable function - short circuit protect (scp) - build in soft start function - 1a shutdown current - tsot23- 5l and tdfn- 6l pb -free packages v?mw`r?y?b? www.gofotech.com
2/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ? b lock d iagram ? pin assignment the package s of AX3513A are tsot23 - 5l and t dfn - 6l; the pin assignment is given by : name desc ription en enable pin h normal operation l shutdown vin power supply input p in sw switch output pin. connect external inductor here. minimize trace area at this pin to reduce emi. gnd ground pin fb output feedback pin nc no connect. f b e n v i n s w g n d o v e r - t e m p e r a t u r e a n d s h o r t - c i r c u i t p r o t e c t i o n r e f s o f t - s t a r 0 . 6 v + - - + i c o m p - + i s e n s e a m p o s c s l o p e c o m p p w m l o g i c n o n - o v e r l a p c o n t r o l r e s e t s e t e n a b l e l o g i c ( top view ) en gnd sw vin fb 1 2 3 4 5 tsot 23 - 5 l t d f n - 6 l ( 2 * 2 ) v i n f b s w 1 2 3 4 5 6 e n g n d n c g n d v?mw`r?y?b? www.gofotech.com
3/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ? order /marking information order information top marking (tsot23 - 5l) top marking ( t dfn - 6 l ) ? a bsolute m aximum r atings (at t a =25 c ) character istics symbol rating unit v in pin voltage v in v ss - 0.3 to 6.5 v feedback pin voltage v fb v ss - 0.3 to v in +0.3 v en pin voltage v en v ss - 0.3 to v in +0.3 v switch pin voltage v sw v ss - 0.3 to v in +0.3 v peak sw sink and source current i ps w 1. 4 a power dissipation pd ( t j - t a ) / ja mw storage temperature range t st - 40 to +150 c operating temperature range t op - 4 0 to + 8 5 c junction temperature t j +125 c thermal resistance from junction to case t dfn - 6l jc 25 c /w tsot 23 110 thermal resistance from junction to ambient t dfn - 6l ja 120 c /w tsot 23 250 note: ja is measured with the pcb copper area of approximately 1 in 2 (multi - layer). that need connect to gnd pin or exposed pad ( AX3513A z 6 ) . p a c k a g e t y p e a x 3 5 1 3 a p a c k i n g a : t a p i n g x x x b t : t s o t 2 3 - 5 l z 6 : t d f n - 6 l ( 2 * 2 ) g w w : 0 1 ~ 2 6 ( a ~ z ) 2 7 ~ 5 2 ( a ~ z ) y e a r : a = 2 0 1 0 1 = 2 0 1 1 i d c o d e : i n t e r n a l a x 3 5 1 3 a b y w x g w w : 0 1 ~ 2 6 ( a ~ z ) 2 7 ~ 5 2 ( a ~ z ) y e a r : a = 2 0 1 0 1 = 2 0 1 1 i d c o d e : i n t e r n a l a x 3 5 1 3 a b y w x v?mw`r?y?b? www.gofotech.com
4/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ? electrical characteristics ( v in = v en =3.6v, t a =25 c , unless otherwise specified ) characteristics symbol conditions min typ max units input voltage range v in 2.5 - 5.5 v feedback voltage v fb t a = +25c 0.588 0.600 0.612 v - 40c t a 85c 0.582 0.600 0.618 feedback bias current i fb v fb =0.65v - - 30 na quiescent current i cc q v fb = 1 v - 250 3 50 ua shutdown supply current i sd v en =0v - 0.1 1 ua switching current limit i limit 1. 2 1. 4 - a line regulation v out /v out v in = 2.5v to 5.5v - 0. 04 0.4 % /v load regulation v out /v out i out = 0.01 to 1 a - 0 . 5 - % oscillation frequency f osc sw pin 1.1 1. 4 1. 7 mhz r ds(on) of p - ch mosfet r dson v fb = 0v, i out = 0.5 a - 0.3 0.4 r ds(on) of n - ch mosfet r dson (note 1) - 0. 2 5 0. 35 en pin logic input threshold voltage v enl - - 0.4 v v enh 1.5 - - en pin in put current i en - 0.1 1 ua efficiency effi v in =5v, v out = 3.3 v, i out =0.5a - 9 4 - % thermal shutdown t ds - 140 - c thermal shutdown hysteresis t sh - 30 - c note 1: guaranteed by design . v?mw`r?y?b? www.gofotech.com
5/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ? a pplication c ircuit ? f unction d escriptions operation AX3513A is a monolithic switching mode step - down dc - dc converter. it utilizes internal mosfets to achieve high efficiency and can generate very low output voltage by using internal reference at 0.6v. it operates at a fixed switching frequency, and uses the slope compens ated current mode architecture. this step - down dc - dc converter su pplies minimum 1000ma output current at input voltage range from 2.5 v to 5.5v. current mode pwm control slope compensated current mode pwm control provides stable switching and cycle- by -cycle current limit for excellent load and line transient responses and protection of the internal main switch (p-ch mosfet) and synchronous rectifier (n-ch mosfet). during normal operation, the internal p-ch mosfet is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. the current comparator, i comp, limits the peak inductor current. when the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, beginning of the next clock cycle. v o u t = 0 . 6 * ( 1 + r 1 / r 2 ) r 2 3 0 0 k c 1 4 . 7 u c 2 1 0 u v o u t = 1 . 8 v r 2 = 5 0 k ~ 3 3 0 k l 1 2 . 2 u h r 1 6 0 0 k u 1 a x 3 5 1 3 a v i n e n g n d s w f b c 3 1 5 p v i n = 2 . 5 v ~ 5 . 5 v v?mw`r?y?b? www.gofotech.com
6/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ? a pplication i nformation setting the output voltage application circuit item shows the basic application circuit with AX3513A adjustable output version. the external resistor sets the output voltage according to the following equation: table 1 resistor select for output voltage setting v out r2 r1 1.2v 30 0 k 30 0 k 1.5v 300k 450k 1.8v 300k 600k 2.5v 15 0k 47 0k 3.3v 120k 540k inductor selection for most designs, the AX3513A operates with inductors of 2.2h to 3.3 h. low inductance values are physically smaller but require faster switching, which results in some efficiency loss. the inductor value can be derived from the following equation: where is inductor ripple current. large value inductors lower ripple current and small value inductors result in high ripple currents. choose inductor ripple current approximately 20 % of the maximum load current 1000ma, i l = 20 0ma. table 2 inductor select for output voltage setting (v in =3.6v) v out 1.2v 1.5v 1.8v 2.5v inductor 2. 2 uh 2. 2 uh 2. 2 uh 2. 2 uh part number we - tpc 7440430022 7440430022 7440430022 7440430022 note: part type mh or m (www.we-online.com) ? ? ? ? ? ? ? ? ? r r v v out ? ? f i v v v v l osc l in out in out ? ? ? ? ? ? v?mw`r?y?b? www.gofotech.com
7/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A for optimum voltage-positioning load transients, choose an inductor with dc series resistance in the 50m? to 150m? range. for higher efficiency at heavy loads (above 200ma), or minimal load regulation (but some transient overshoot), the resistance should be ke pt below 100m?. the dc current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation ( 1000ma+ 10 0ma). input capacitor selection the input capacitor reduces the surge current drawn from the input and switching noise from the device. the input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input. a low esr input capacitor sized for maximum rms current must be used. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. a 4.7 f ceramic capacitor for most applications is sufficient. output capacitor selection the output capacitor is required to be 10uf to keep the output voltage ripple small and to ensure regulation loop stability. the output capacitor must have low impedance at the switching frequency. ceramic capacitors with x5r o r x7r dielectrics are recommended due to their low esr and high ripple current. compensation capacitor selection the compensation capacitors for increasing phase margin provide additi onal stability. it is required 15 p f , please r efer to demo board schemat ic to design . v?mw`r?y?b? www.gofotech.com
8/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A t sot23 - 5l layout guide tdfn- 6l layout guide e n g n d s w f b v i n c 1 v i n g n d l 1 v o u t c 2 r 1 r 2 s w s h o u l d b e c o n n e c t e d t o i n d u c t o r b y w i d e a n d s h o r t t r a c e , k e e p s e n s i t i v e c o m p o n e n t s a w a y f r o m t h i s t r a c e c 2 a x 3 5 1 3 a 1 2 3 4 5 g n d c 2 ' s g r o u n d m u s t b e a s c l o s e r t o i c ' s g n d p i n a s p o s s i b l e v i n c 1 ' s g r o u n d m u s t b e a s c l o s e r t o i c ' s g n d p i n a s p o s s i b l e c 2 , r 1 a n d r 2 m u s t b e a s c l o s e r t o i c ' s f b p i n a s p o s s i b l e gnd nc 1 2 4 5 6 en sw fb ep 3 vin c 1 vin gnd l 1 vout c 2 r 1 r 2 sw should be connected to inductor by wide and short trace , keep sensitive components away from this trace c 2 gnd c 1 and c 2 ' s ground must be as close r to ic ' s gnd pin as possible c 2 , r 1 and r 2 must be as close r to ic ' s fb pin as possible and keep the switching trace away . v?mw`r?y?b? www.gofotech.com
9/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ? typical characteristics v?mw`r?y?b? www.gofotech.com
10/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ? typical characteristics (c ontinues ) v?mw`r?y?b? www.gofotech.com
11/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ? typical characteristics (continues) v in = 5v, v out = 1.2v, r load = no load v in = 5v, v out = 1.2v, r load = 1? v in = 5v, v out = 1.2v, r load = no load v in = 5v, v out = 1.2v v in = 5v, v out = 1.2v, i out = 0 a ? 1a v in = 3.3 v, v out = 1.2 v, i out = 0 a ? 1a v?mw`r?y?b? www.gofotech.com
12/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ? p ackage o utlines ( 1 ) tsot23 - 5l symbol dimensions in milli meters dimensions in inches min. nom. max. min. nom. max. a - - 1.1 - - 0.043 a1 0 - 0.1 0 - 0.004 a2 0.7 0.9 1 0.028 0.035 0.039 b 0.3 0.4 0.5 0.012 0.016 0.02 c 0.08 0.14 0.2 0.003 0.006 0.008 d 2.8 2.9 3 0.11 0.114 0.118 e 2.6 2.8 3 0.102 0.11 0.118 e1 1.5 1.6 1.7 0.059 0.063 0.067 e 0.95 bsc. 0.037 bsc. e1 1.90 bsc. 0.075 bsc. l 0.3 0.45 0.6 0.012 0.018 0.024 l1 0.60 ref. 0.024 ref. l2 0.25 bsc. 0.010 bsc. y - - 0.1 - - 0.004 r 0.1 - - 0.004 - - 0 o - 8 o 0 o - 8 o jeced outline: mo - 193 ab e 1 e e e 1 b d a a 1 a 2 y l 1 r l c l 2 v?mw`r?y?b? www.gofotech.com
13/ 13 axelite confidential materials, do not copy or distribute without written consent. rev. 1. 0 oct . 14 , 20 11 AX3513A ( 2 ) t dfn - 6l ( 2*2 0.75mm ) symbol dimensions in millimeters dimensions in inches min. nom. max. min. nom. max. a 0.7 0.75 0.8 0.028 0.03 0.031 a1 0 0.02 0.05 0 0.001 0.002 a3 0.203 ref. 0.008 ref. b 0.2 0.28 0.35 0.009 0.011 0.013 d 1.95 2 2.05 0.077 0.079 0.081 d2 1.35 1.5 1.65 0.055 0.059 0.063 e 1.95 2 2.05 0.077 0.079 0.081 e2 0.75 0.9 1.05 0.031 0.035 0.039 e 0.65 bsc. 0.026 bsc. l 0.2 0.3 0.4 0.008 0.012 0.016 e d a a 1 a 3 d 2 e e 2 ( t o p v i e w ) ( b o t t o m v i e w ) b p i n 1 l s e a t i n g p l a n e ( s i d e v i e w ) v?mw`r?y?b? www.gofotech.com

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