1/8 ax elite confidential materials, do not copy or distribute without written consent . rev.1.6 oct.24, 2011 a x2002 /a 2a, 0.25v feedback v oltage step-down switching regulators for led driver ? general description AX2002/a consists of step-dow n switching regulator with pwm control. these devise include a reference voltage source, oscillation circuit, error amplifier, internal pmos and etc. AX2002/a provides low-rippl e power, high efficiency, and excellent transient characteristics. the pwm control circuit is abl e to the duty ratio linearly from 0 up to 100%. an enable function, an over cu rrent protect function and short circuit protect function are built inside, and when ocp or scp happens, t he operation frequency will be reduced. also, an internal compensation block is built in to minimum external component count. with the addition of an internal p-channel po wer mos, a coil, capacitors, and a diode connected externally, these ics can function as step-down switching regulators. they serve as ideal power supply units for portable dev ices when coupled with the sop-8l package, providing such outstanding features as low current consum ption. since this converter can accommodate an input voltage up to 23v, it is also suitable for the operation via an ac adapter. ? fea tures - input voltage 3.6v to 23v - output voltage 0.25v to v cc - led back light and high power led application - duty ratio 0% to 100% pwm control - oscillation frequency AX2002: 330khz typ. AX2002a: 500khz typ. - enable/disable function. - current limit (cl), thermal shutdown and short circuit protections (scp). - built-in internal sw p-channel mos. - no output capacitor is stable. - sop-8l pb-free package. v?mw`r?y?b? w w w . g o f o t e c h . c o m
2/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.6 oct.24, 2011 a x2002 / a ? block diagram vcc oscillator circuit reference voltage pwm switched control circuit + - vss v en en comp fb thermal shutdown sw current limit ? pin assignmet the package of AX2002/a is sop-8l; the pin assignment is given by: ( top view ) 1 2 3 4 8 7 6 5 fb sw comp sop-8l AX2002/a sw en vss vss vcc name description fb feedback pin en power-off pin h normal operation(step-down) l step-down operation stopped (all circuits deactivated) comp compensation pin v cc ic power supply pin sw switch pin. connect external inductor/diode here. v ss gnd pin ? order/marking information order information top marking package type s: sop-8l AX2002 x x x packing a : taping blank : tube frequecny a : 500khz blank : 330khz a ax 2 logo part number id code: internal ww: 01~52 year: 10=2010 11=2011 AX2002a y y ww x 00 2 v?mw`r?y?b? w w w . g o f o t e c h . c o m
3/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.6 oct.24, 2011 a x2002 / a ? absolute maximum ratings (at t a =25 c ) characteristics symbol rating unit v cc pin voltage v cc v ss - 0.3 to v ss + 25 v feedback pin voltage v fb v ss - 0.3 to v cc v on/off pin voltage v en v ss - 0.3 to v cc + 0.3 v switch pin voltage v sw v ss - 0.3 to v cc + 0.3 v power dissipation pd internally limited mw storage temperature range t st -40 to +150 c operating temperature range t op -40 to +125 c operating supply voltage v op +3.6 to +23 v thermal resistance from junction to case jc 25 c/w thermal resistance from junction to ambient ja 70 c/w note : e ja is measured with the pcb copper area(need connect to sw pins) of approximately 1 in 2 (multi-layer). ? electrical characteristics (v in = 12v, t a =25c, unless otherwise specified) characteristics symbol conditions min typ max units feedback voltage v fb i out =0.2a 0.24 0.25 0.26 v quiescent current i ccq v fb =1.2v force driver off 3 5 ma feedback bias current i fb i out =0.1a - 0.1 0.5 ua shutdown supply current i sd v en =0v - 2 10 ua switch current i sw 2.5 - - a line regulation v out /v out v cc =5v~23v, i out =0.2a - 1 2 % load regulation v out /v out i out =0.1 to 2a - 0.2 0.5 % oscillation frequency f osc AX2002 260 330 400 khz AX2002a 400 500 600 khz en pin logic 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) - -10 - ua internal mosfet r dson r dson v cc =5v, v fb =0v - 100 140 m ? v cc =12v, v fb =0v - 70 100 efficiency effi v out = 5v i out =1a - 91 - % i out =2a - 91 - thermal shutdown temp t sd - 140 - c v?mw`r?y?b? w w w . g o f o t e c h . c o m
4/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.6 oct.24, 2011 a x2002 / a ? application circuit a. 1w/3w led*1 for dc input vout vcc r1 100k u1 AX2002/a 1 2 3 4 5 6 7 8 fb en comp vcc sw sw vss vss d7 led r2 0.75r/0.33r r4 4.7k c4 1u l1 22uh (10uh for AX2002a) d6 1n4148 d5 b240a c3 0.1u r5 100k c2 22u c1 4.7u option 1w/3w b. 1w/3w led*1 for ac input (1) no output capacitor vout u1 AX2002/a 1 2 3 4 5 6 7 8 fb en comp vcc sw sw vss vss d2 led r2 c5 l1 d5 b240a r5 100nf c2 ac 12v in ac d4 ac d3 ac d2 ac d1 c3 0.1u part no. i led r2 c2 r5 l1 AX2002 350ma 0.715 ? 87.5mw 100uf 0.22k 68uh 750ma 0.333 ? 189mw 220uf 0.47k 1000ma 0.250 ? 250mw 330uf 0.47k AX2002a 350ma 0.715 ? 87.5mw 100uf 0.22k 47uh 750ma 0.333 ? 189mw 220uf 0.47k 1000ma 0.250 ? 250mw 330uf 0.47k v?mw`r?y?b? w w w . g o f o t e c h . c o m
5/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.6 oct.24, 2011 a x2002 / a (2) add 4.7uf output capacitor vout u1 AX2002/a 1 2 3 4 5 6 7 8 fb en comp vcc sw sw vss vss d2 led r2 c5 l1 d5 b240a r5 c2 ac 12v in ac d4 ac d3 ac d2 ac d1 c3 0.1u c1 4.7u c4 100r 100n part no. i led r2 c2 c4 l1 AX2002 350ma 0.715 ? 87.5mw 100uf 10nf 33uh 750ma 0.333 ? 189mw 220uf 1000ma 0.250 ? 250mw 330uf AX2002a 350ma 0.715 ? 87.5mw 100uf 3.3nf 22uh 750ma 0.333 ? 189mw 220uf 1000ma 0.250 ? 250mw 330uf ? function descriptions pwm control the AX2002/a consists of dc/dc converters that employ a pulse-width modulation (pwm) system. in converters of the AX2002/a, t he pulse width varies in a range from 0 to 100%, according to the load current. the ri pple voltage produced by the switching can easily be removed through a filter becaus e the switching frequency remains constant. therefore, these converters provide a low-ri pple power over broad r anges of input voltage and load current. setting the i led current application circuit item shows the basic application circuit with AX2002/a adjustable output version. the external resistor sets the led output current according to the following equation: ? ? ? ? ? ? ? 2 25.0 r v i led v?mw`r?y?b? w w w . g o f o t e c h . c o m
6/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.6 oct.24, 2011 a x2002 / a table 1 resistor select fo r led output current setting i led r2 350ma 0.715 ? 87.5mw 750ma 0.333 ? 189mw 1000ma 0.250 ? 250mw rds (on) current limiting the current limit threshold is setting by the internal circuit. compensation please refer the table of application circ uit. for dc input, the option circuit for compensation is connecting r4 and a 4148 diode to v out . in order to protect short circuit and thermal shutdown release for led. pcb layout guide if you need low tc and tj or large pd (power dissipation), the dual sw pins (5 and 6) on the sop-8l package are inter nally connected to die pad, the pcb layout should allow for maximum possible copper area at the sw pins of the AX2002/a. v?mw`r?y?b? w w w . g o f o t e c h . c o m
7/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.6 oct.24, 2011 a x2002 / a ? typical characteristics v?mw`r?y?b? w w w . g o f o t e c h . c o m
8/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.6 oct.24, 2011 a x2002 / a ? package outlines symbol dimensions in millimeters dimensions in inches min. nom. max. min. nom. max. a - - 1.75 - - 0.069 a 1 0.1 - 0.25 0.04 - 0.1 a 2 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 v?mw`r?y?b? w w w . g o f o t e c h . c o m
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