1 / 8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 1 aug . 2 4 , 20 10 ax 5 3 0 2 pwm step - up con tro ller ? general description the AX5302 is high efficient pwm step - up controll er. designed to drive an ex ternal n - channel mosfet , output voltage is programmable with 1.0v of standard voltage supply internal, and using externally connected com ponents, output voltage (fb) can be set up at will. the AX5302 can be operated at switching frequenc ies of 5 00khz allowing for easy filtering and low noise , the size of the external components can be reduced. an enable function and thermal shutdown functio ns are built inside. the soft - start time can be programmed by outside capacitor; the function prevents overshoot at startup. ? features - input voltage: 3.0 v to 2 4 v - output voltage: define by n - channel mos - duty ratio: 0% to 8 5 % pwm control - oscillation frequency : 5 00khz ( 2 0 % ) - soft - start time is programmed by outside capacitor - current limit is setting by outside resistance - t hermal shutdown protection - enable /shutdown function - external sw n - channel mos. - sop - 8l pb - free package. ? b lock d iagram + - oscillator buffer driver fb gnd vcc gate phase compensation + - pwm controller en thermal shutdown sense 0 . 06 v 8 ua ss v en vref = 1 . 0 v regulator + - oscillator buffer driver fb gnd vcc gate phase compensation + - pwm controller en thermal shutdown sense 0 . 06 v 8 ua ss v en vref = 1 . 0 v regulator
2 / 8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 1 aug . 2 4 , 20 10 ax 5 3 0 2 ? pin assignment this package of AX5302 is sop - 8l ; the pin assignment is given by : name description en shutdown control input. h fb feedback pin v cc vcc supply pin sense current lim it sense voltage ss soft - start pin gate gate drive for external n - channel mosfet. gnd signal ground pin nc no connection ? order/marking information order information top marking ? a bolute m a ximum r atings (at t a =25 c ) characteristics symbol rating unit vcc pin voltage v cc v ss - 0.3 to v ss + 2 6 v feedback pin voltage v fb v ss - 0.3 to 12 v en voltage v en v ss - 0.3 to v cc v sense voltage v sense v ss - 0.3 to v cc v ss pin voltage v ss v ss - 0.3 to v cc v gate pin voltage v gate v ss - 0.3 to v cc v power dissipation pd internally limited mw storage temperature range t st - 40 to +150 c operating junction temperature range t op j - 2 0 to +1 25 c operating supply voltage v op +3 to +24 v thermal resi stance from junction to case jc 40 c /w thermal resistance from junction to ambient ja 120 c /w note : ja is measured with the pcb copper area of approximately 1 in 2 (multi - layer) . ( top view ) 1 2 3 4 8 7 6 5 a x 5 3 0 2 en ss vcc gate nc sense sop - 8 l fb gnd package type s : sop - 8 l ax 5302 x x packing blank : tube a : taping logo y ax 5 part number id code : internal ww : 01 ~ 52 year : 10 = 2010 11 = 2011 3 0 2 y w w x
3 / 8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 1 aug . 2 4 , 20 10 ax 5 3 0 2 ? e lectrical c haracterustics (v in = 5 v, v out = 12 v, t a = 25 c , unless otherwise specified) character istics symbol conditions min typ max units feedback voltage v fb i out =0.1a 0. 9 75 1.0 00 1.02 5 v quiescent current i ccq v fb =1. 5 v force driver off - 4 6 ma feedback bias current i fb i out =0.1a - 0.1 0.5 ua shutdown supply current i sd v en =0v - 1 10 ua osci llation frequency f osc sw pin 40 0 5 00 60 0 khz s e nse voltage v sense 0 .0 5 0.0 6 0.0 7 v soft start current i ss v ss =0v - 8 - ua en pin l ogic input threshold voltage v sh high (regulator on) 2.0 - - v v sl low (regulator off) - - 0.8 en pin input current i sh v en =2.5v (on) - 20 - ua i sl v en =0.3v (off) - - 1 - ua lx rise time t lxr c lx =1000pf - 6 0 - ns lx fall time t lxf c lx =1000pf - 6 0 - efficiency effi v cc = 5 v, v out = 12v i out = 1 a - 9 1 - % maximum duty cycle dc max v fb =0v - 8 5 - % minimum duty cycle dc min v fb = 1.5 v - 0 - thermal shutdown temp t sd - 1 4 5 - c ? a pplication c ircuit v out = v fb (1 + ), v fb = 1.0v, r2 = 1k ~ 3k c4 capacitor esr suggest 30m~100m c 2 0 . 1 uf q 1 nmos c 4 470 uf c 5 0 . 1 uf r 2 1 k c 1 470 uf d 1 b 340 a l 1 15 uh vcc = 5 v u 1 ax 5302 1 7 2 8 5 3 6 4 ss en vcc sense gnd gate r 1 11 k c 3 4 . 7 u vout = 12 v / 1 . 0 a r 3 100 k fb r sense 0 . 02 c 6 0 . 1 uf nc ? r2 r1
4 / 8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 1 aug . 2 4 , 20 10 ax 5 3 0 2 ? f unction d escriptions pwm control the AX5302 is high efficient pwm step - up controller. in controllers of the AX5302, the pulse width varies in a range from 0 to 85%, according to the load current. the ripple voltage produced by the switching can easi ly be removed through a filter because the switching frequency remains constant. therefore, AX5302 provide a low - ripple power over broad ranges of input voltage and load current. setting the output voltage application circuit item shows the basic applica tion circuit with AX5302 adjustable output version. the external resistor sets the output voltage accor ding to the following equation: table 1 resistor select for output voltage setting v out r2 r1 12v 1 k 11 k 15v 1.5 k 21 k 18v 1 k 1 7 k 24 v 1.3 k 30 k current limiting setting the current limit threshold is setting by the external resistor (r sense ) connecting fro m sense pin to gnd (refer the application circuit) . the internal current limit compared voltage is 60mv. when the sense volt age is larger than 60mv , an over - current condition is triggered. please refer to the formula for setting the minimum current limit value : note: i sw (max) is the maximum n - mosfet current. ? ? ? ? ? ? ? ? ? 2 1 1 0 . 1 r r v v out rsense 60m i sw(max) ?
5 / 8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 1 aug . 2 4 , 20 10 ax 5 3 0 2 inductor selection for most design s, 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 induc tors lower ripple current and small value inductors result in high ripple currents. choose inductor ripple current approximately 15 % of the maximum input current 3 a, i l = 0.45 a. table 2 inductor select for output voltage setting (v cc = 5 v) v out 9v 12v 15v 18v l1 value 18 u h 15uh 10uh 10uh the dc current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent c ore saturation ( 3 a+ 0.25 a). 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 impedan ce to prevent high frequency switching current passing to the input. a low esr input capacitor sized for maximum rms current must be used . the capacitor voltage rating should be at least 1.5 times greater than the in put voltage, and often much higher volta ge ratings are needed to satisfy . ? ? f i v v v v l lx l out in out in ? ? ? ? ? ?
6 / 8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 1 aug . 2 4 , 20 10 ax 5 3 0 2 output capacitor selection the output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. the output capacitor must have low impedance at the switching frequen cy. a low esr capacitor sized for maximum rms current must be used . the low esr requirements needed for low output ripple voltage. the capacitor voltage rating should be at least 1.5 times greater than the input voltage, and often much higher voltage ratin gs are needed to satisfy. the es r range of output capacitor is 3 0m~100m at switch current more than 1.5a. add a 4.7uf output bypass capacitor in order to reduce output ripple effectively. layout guidance when laying out the pc board, the following sugge stions should be taken to ensure proper operation of the AX5302 . these items are also illustrated graphically in below . 1. the power traces, including the nmos drain & source trace, the inductor and the c1 trace should be kept short, direct and wide to all ow large current flow. 2. the ground area for r sense and c1 must be closed and c2 closed vcc pin of AX5302 to get good stability. 3. keep the switching node , away from the sensitive fb node. 4. do not trace signal line under inductor.
7 / 8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 1 aug . 2 4 , 20 10 ax 5 3 0 2 ? typical characteristucs power - on wave (v cc =5v, v out =12v, load=0.7a, ss=0.1uf) enable - on wave (v cc =5v, v out =12v, load=0.7a, ss=0.1uf) 11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13 3 4 5 6 7 8 9 10 vcc (v) vout (v) vcc vs vout iout=0.1a 11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13 0 100 200 300 400 500 600 iout (ma) vout (v) iout vs vout vcc=5v 0 1 2 3 4 5 6 7 8 9 10 -50 -25 0 25 50 75 100 temperature () shutdown current (ua) temperature vs shutdown current vcc=20v 0.95 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.05 -50 -25 0 25 50 75 100 temperature () vfb (v) temperature vs vfb
8 / 8 axelite confidential materials, do not copy or distribute without written consent . rev. 1. 1 aug . 2 4 , 20 10 ax 5 3 0 2 ? p ackage o utlines symbol dimensions in millimeters dimensions in inches min. nom. max. min. nom. max. a - - 1.75 - - 0.069 a1 0.1 - 0.25 0.04 - 0.1 a2 1.25 - - 0.049 - - c 0.1 0.2 0.25 0.0075 0.008 0.01 d 4.7 4.9 5.1 0.185 0.193 0.2 e 3.7 3.9 4.1 0.146 0.154 0.161 h 5.8 6 6.2 0.228 0.236 0.244 l 0.4 - 1.27 0.015 - 0.05 b 0.31 0.41 0.51 0.012 0.016 0.02 e 1.27 bsc 0.050 bsc y - - 0.1 - - 0.004 0 o - 8 o 0 o - 8 o mold flash shall not exceed 0.25mm per side jedec outline: ms - 012 aa detail a l h e a a 2 a 1 e d 7 ( 4 x ) b y c detail a
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