1/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.5 sep.03, 2009 AX4102 pwm control 3.5a step-down converter ? general description AX4102 consists of step-down switchin g regulator with pwm control. these devise include a reference voltage source, osc illation circuit, error amplifier, internal pmos and etc. AX4102 provides low-ripple power, hi gh efficiency, and excellent transient characteristics. the pwm control circuit is able to the duty ratio linearly form 0 up to 100%. an enable function, an over current pr otect function and short circuit protect function are built inside, and when oc p or scp happens, t he operation frequency will be reduced. also, an internal compensati on block is built in to minimum external component count. with the addition of an internal p-channel power mos, a coil, capacitors, and a diode connected externally, these ics can f unction as step-down switching regulators. they serve as ideal power supply units fo r portable devices when coupled with the sop-8l package, providing such outstanding features as low current consumption. since this converter can accommodate an input voltage up to 23v, it is also suitable for the operation via an ac adapter. ? features - input voltage 3.6v to 23v - output voltage 0.8v to vcc - duty ratio 0% to 100% pwm control - oscillation frequency 330khz typ. - current limit(cl), enable function. - thermal shutdown function. - short circuit protect (scp). - built-in internal sw p-channel mos. - sop-8l pb-free package. n?tuf?m?w3^v?mw`r?y?b?g ?pqls? www.gofotech.com tel: 0755-6135 8291/8292 www..net
2/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.5 sep.03, 2009 pwm control 3.5a step-down converter AX4102 ? block diagram vcc oscillation circuit reference voltage + - vss v en en ocset fb sw thermal shutdown 110ua - pwm switched control circuit ? pin assignment the package of AX4102 is sop-8l; t he pin assignment is given by: name description fb feedback pin en power-off pin h normal operation(step-down) l step-down operation stopped (all circuits deactivated) ocset add an external resistor to set max switch output current. v cc ic power supply pin sw switch pin. connect external inductor & diode here. ( top view ) 1 2 3 4 8 7 6 5 fb ocset sop C 8l AX4102 vcc en vss vss sw sw v ss gnd pin ? order/marking information order information top marking x x x x x ax 4102 logo part number id code: internal ww: 01~52 year : 06 = 2006 n?tuf?m?w3^v?mw`r?y?b?g ?pqls? www.gofotech.com tel: 0755-6135 8291/8292 www..net
3/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.5 sep.03, 2009 pwm control 3.5a step-down converter AX4102 ? absolute maximum ratings (at ta=25 ) characteristics symbol rating unit vcc 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 operating junction temperature range t j -20 to +125 operating supply voltage v op +3.6 to +23 v output current i out 0 to 3.5 a peak current i peak 6.0 a thermal resistance from junction to case jc 25 /w thermal resistance from junction to ambient ja 70 /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 (vin = 12v, v out =3.3v, ta=25 , unless otherwise specified) characteristics symbol conditions min typ max units feedback voltage v fb i out =0.1a 0.784 0.8 0.816 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 ocset pin bias current i ocset 110 130 150 ua switch current i sw 4.5 - - a line regulation v out /v out v cc = 8v~23v, i out =0.2a - 1 2 % load regulation v out /v out i out = 0.1 to 3.5a - 0.2 0.5 % oscillation frequency f osc sw pin 260 330 400 khz v sh high (regulator on) 2.0 - - en pin logic input threshold voltage v sl low (regulator off) - - 0.8 v i sh v en =2.5v (on) - 20 - ua en pin input current i sl v en =0.3v (off) - -10 - ua v cc =5v, v fb =0v - 80 140 internal mosfet r dson r dson v cc =12v, v fb =0v - 55 90 m? i out = 2a 92 efficiency effi v cc = 12v, v out = 5v i out = 3.5a - 90 - % n?tuf?m?w3^v?mw`r?y?b?g ?pqls? www.gofotech.com tel: 0755-6135 8291/8292 www..net
4/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.5 sep.03, 2009 pwm control 3.5a step-down converter AX4102 ? application circuit r1 r2 vfb = 0.8v ; r2 suggest 0.8k ~ 6k vout = vfb x (1 + ) c2 470uf c3 0.1uf c4 470uf 1 2 l1 22uh r1 30k r2 5.6k vin+12v on/off c1 1nf vout = 5v/3.5a r3 1.5k r4 100k d1 b340 c8 0.1uf fb 1 en 2 ocset 3 vcc 4 sw 5 sw 6 vss 7 vss 8 AX4102 c6 0.1uf l1 recommend value (v in =12v ) v out 1.8 v 2.5v 3.3v 5v i out =3.5a 12uh 15uh 18uh 22uh ? function descriptions pwm control the AX4102 consists of dc/dc converters that employ a pulse-width modulation (pwm) system. in converters of the AX4102, the 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 because the switching frequency remains constant. therefore, these converters provide a lo w-ripple power over broad ranges of input voltage and load current. rds(on) current limiting the current limit threshold is setting by t he external resistor (r3) connecting from v cc supply to ocset pin. the internal 130ua sink current crossing the resistor sets the voltage at pin of ocset. when the pwm volt age is less than the voltage at ocset, an over-current condition is trigger ed. please refer to the formula for setting the current limit value: r i i ds(on) ocset sw(min) 08.0r3 + = (normally, the i sw(max) setting more than i out 1.0a ). example: i sw = (0.13ma x 1.5k + 0.08)/ 0.055= 5a (vin=12v) i sw = (0.13ma x 2.7k + 0.08)/ 0.080= 5.39a (vin=5v) n?tuf?m?w3^v?mw`r?y?b?g ?pqls? www.gofotech.com tel: 0755-6135 8291/8292 www..net
5/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.5 sep.03, 2009 pwm control 3.5a step-down converter AX4102 setting the output voltage application circuit item shows the basic application circuit with AX4102 adjustable output version. the external resistor sets the output voltage according to the following equation: ? ? ? ? ? ? += 2 1 18.0 r r v v out table 1 resistor select for output voltage setting v out r2 r1 1.3k 6.8k 5v 5.6k 30k 1.5k 4.7k 3.3v 5.6k 18k 2.2k 4.7k 2.5v 5.6k 12k 1.8v 2k 2.5k 1.5v 2.2k 2.0k 1.2v 3k 1.5k 1.0v 3k 0.75k r2 setting 5.6k that system operation curr ent (no load) can be r educing to under 4ma. c2 470uf c3 0.1uf c4 470uf 1 2 l1 22uh r1 30k r2 5.6k vin>+9v on/off c1 1nf vout = 5v/3.5a r3 1.5k r4 100k d1 b340 c8 0.1uf fb 1 en 2 ocset 3 vcc 4 sw 5 sw 6 vss 7 vss 8 AX4102 c6 0.1uf pcb layout guide if you need low tc & tj or large pd(power dissipation), the dual sw pins(5&6) on the sop-8l package are internally connected to die pad, the pcb layout should allow for maximum possible copper area at the sw pins. 1. connect c3 to v cc pin as closely as possible to get good power filter effect. 2. connect r3 to v cc pin as closely as possible. 3. connect ground side of the c2 & d1 as closely as possible. n?tuf?m?w3^v?mw`r?y?b?g ?pqls? www.gofotech.com tel: 0755-6135 8291/8292 www..net
6/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.5 sep.03, 2009 pwm control 3.5a step-down converter AX4102 ? typical characteristics vfb vs vin iccq vs vin vfb vs vin 0.780 0.784 0.788 0.792 0.796 0.800 0.804 0.808 0.812 0.816 0.820 4 6 8 10 12 14 16 18 20 22 24 vfb (v) vin (v) iccq vs vin 0.0 1.0 2.0 3.0 4.0 5.0 6.0 4 6 8 1012141618202224 vin (v) iccq (ma) fosc vs vin fosc vs temperature fosc vs vin 280.0 290.0 300.0 310.0 320.0 330.0 340.0 350.0 360.0 4 6 8 1012141618202224 vin (v) f osc (khz ) fosc vs temperature 280.0 290.0 300.0 310.0 320.0 330.0 340.0 350.0 360.0 -20 0 20 40 60 80 100 120 temp ( ) fosc(khz) vfb vs temperature iccq vs temperature vfb vs temperature 0.780 0.785 0.790 0.795 0.800 0.805 0.810 0.815 0.820 -20 0 20 40 60 80 100 120 temp ( ) vfb(v) iccq vs temperature 0.0 1.0 2.0 3.0 4.0 5.0 6.0 -20 0 20 40 60 80 100 120 temp ( ) iccq(ma ) n?tuf?m?w3^v?mw`r?y?b?g ?pqls? www.gofotech.com tel: 0755-6135 8291/8292 www..net
7/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.5 sep.03, 2009 pwm control 3.5a step-down converter AX4102 ? typical characteristics output ripple (v in =12v, v out =5v, i out =3a) power on test wave (v in =12v, v out =5v, i out =3a ) load transient response (v in =12v, v out =5v, i out =0.1~3a) en pin on test wave (v in =12v, v out =5v, i out =3a ) efficiency (v in =12v, v out =5v) efficiency (v in =12v, v out =3.3v) vou t=5 v 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.0 1.0 2.0 3.0 iout(a) efficiency(%) vou t=3 .3 v 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.0 1.0 2.0 3.0 iout(a) efficiency(%) sw sw i sw v out v in sw i sw sw i sw v out v in v out (ac) v out v out (ac) i sw n?tuf?m?w3^v?mw`r?y?b?g ?pqls? www.gofotech.com tel: 0755-6135 8291/8292 www..net
8/8 axelite confidential materials, do not copy or distribute without written consent . rev.1.5 sep.03, 2009 pwm control 3.5a step-down converter AX4102 ? package outlines detail a l h e a a2 a1 e d 7 (4x) b y c detail a dimensions in millimeters dimensions in inches symbol min. nom. max. min. nom. max. a 1.40 1.60 1.75 0.055 0.063 0.069 a1 0.10 - 0.25 0.040 - 0.100 a2 1.30 1.45 1.50 0.051 0.057 0.059 c 0.19 0.20 0.25 0.0075 0.008 0.010 d 4.80 4.90 5.00 0.189 0.193 0.197 e 3.80 3.90 4.00 0.150 0.154 0.157 h 5.79 5.99 6.20 0.228 0.236 0.244 l 0.38 0.71 1.27 0.015 0.028 0.050 b 0.33 0.41 0.51 0.013 0.016 0.020 e 1.27 typ 0.050 typ y - - 0.10 - - 0.004 0 o - 8 o 0 o - 8 o n?tuf?m?w3^v?mw`r?y?b?g ?pqls? www.gofotech.com tel: 0755-6135 8291/8292 www..net
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