1/8 axelite confidential materials, do not copy or distribute without written consent . rev.2.0 aug.09, 2010 AX3102 pwm control 3a step-down converter ? general description AX3102 consists of step-down switching r egulator with pwm control. these devise include a reference voltage source, oscillation circuit, error amplifier, internal pmos and etc. AX3102 provides low-ripple power, high efficiency, and excellent transient characteristics. the pwm control circuit is abl e to every the duty ratio linearly form 0 up to 100%. this converter also contains an error amp lifier circuit as well as a soft-start circuit that prevents overshoot at st artup. an enable function, an ov er current protect function and short circuit protect function are built in side, and when ocp or scp happens, the operation frequency will be reduced. also, an internal co mpensation 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 function as step-down switching r egulators. they serve as ideal power supply units for portable devic es 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. ? features - input voltage 3.6v to 23v - output voltage 0.8v to v cc - duty ratio 0% to 100% pwm control - oscillation frequency 330khz typ. - soft-start (ss), current li mit (cl), enable function. - thermal shutdown function. - short circuit protect (scp). - built-in internal sw p-channel mos. - sop-8l pb-free package.
2/8 axelite confidential materials, do not copy or distribute without written consent . rev.2.0 aug.09, 2010 AX3102 ? block diagram vcc oscillation circuit reference voltage source with soft start + - vss v en en ocset fb sw thermal shutdown 110ua - pwm switched control circuit ? pin assignment the package of AX3102 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. v ss gnd pin ? order/marking information order information top marking package type s: sop-8l AX3102 x x x packing blank : tube a : taping frequency blank : 330khz logo y ax 3 part number id code:internal ww: 01~52 year: 10=2010 11=2011 1 02 ywwx
3/8 axelite confidential materials, do not copy or distribute without written consent . rev.2.0 aug.09, 2010 AX3102 ? absolute maximum ratings (at t a =25c) characteristics symbol rating unit vcc pin volta g e v cc v ss - 0.3 to v ss + 25 v feedback pin volta g e v fb v ss - 0.3 to v cc v on/off pin volta g e v en v ss - 0.3 to v cc + 0.3 v switch pin volta g e v sw v ss - 0.3 to v cc + 0.3 v power dissipation pd internall y limited mw stora g e temperature ran g e t st -40 to +150 c operatin g junction temperature ran g e t j -20 to +125 c operatin g suppl y volta g e 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: 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, v out =3.3v, t a =25c, 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 4.0 - - 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 3a - 0.2 0.5 % oscillation frequency f osc sw pin 260 330 400 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 soft-start time t ss 0.3 4 8 ms internal mosfet r dson r dson v cc =5v, v fb =0v - 90 140 m ? v cc =12v, v fb =0v - 55 90 efficiency effi v cc = 12v, v out = 5v i out = 2a - 92 - % i out = 3a 91
4/8 axelite confidential materials, do not copy or distribute without written consent . rev.2.0 aug.09, 2010 AX3102 ? 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/3a r3 1.3k r4 100k d1 b340 c8 0.1uf fb 1 en 2 ocset 3 vcc 4 sw 5 sw 6 vss 7 vss 8 AX3102 l1 recommend value (v in =12v ) v out 1.8 v 2.5v 3.3v 5v i out =3a 12uh 15uh 18uh 22uh ? function descriptions pwm control the AX3102 consists of dc/dc converte rs that employ a pulse-width modulation (pwm) system. in converters of the AX3102, 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. 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 cu rrent crossing the resist or sets the voltage at pin of ocset. when the pwm voltage is less than the voltage at ocset, an over-current condition is tri ggered. please refer to the form ula for setting the current limit value: ) on ( ds ocset ) max ( sw r 095 . 0 + 3 r i = i (normally, the i sw(max) setting more than i out 1.0a ). example: i sw = (0.13ua x 1.3k + 0.095)/ 0.055=4.8a i sw = (0.13x 1.3 + 0.095)/ 0.055= 4.8a
5/8 axelite confidential materials, do not copy or distribute without written consent . rev.2.0 aug.09, 2010 AX3102 setting the output voltage application circuit item shows the basic application circuit with AX3102 adjustable output version. the external resistor sets the output voltage according to the following equation: ? ? ? ? ? ? ? ? ? 2 1 1 8 . 0 r r v v out table 1 resistor select for output voltage setting v out r2 r1 5v 1.3k 6.8k 5.6k 30k 3.3v 1.5k 4.7k 5.6k 18k 2.5v 2.2k 4.7k 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 educe 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/3a r3 1.3k r4 100k d1 b340 c8 0.1uf fb 1 en 2 ocset 3 vcc 4 sw 5 sw 6 vss 7 vss 8 AX3102 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 internally connect ed 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 and d1 as closely as possible.
6/8 axelite confidential materials, do not copy or distribute without written consent . rev.2.0 aug.09, 2010 AX3102 ? typical characteristics vfb vs vin iccq vs vin vfb vs vin 0.780 0.785 0.790 0.795 0.800 0.805 0.810 0.815 0.820 3 5 7 9 11 13 15 17 19 21 23 25 vin(v) vfb(v) iccq vs vin 0.0 1.0 2.0 3.0 4.0 5.0 6.0 3 5 7 9 11 13 15 17 19 21 23 25 vin(v) iccq(ma ) fosc vs vin fosc vs temperature fosc vs vin 280.0 290.0 300.0 310.0 320.0 330.0 340.0 350.0 360.0 370.0 380.0 3 5 7 9 11 13 15 17 19 21 23 25 vin(v) fosc(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 )
7/8 axelite confidential materials, do not copy or distribute without written consent . rev.2.0 aug.09, 2010 AX3102 ? typical characteristics (continuous) 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(%)
8/8 axelite confidential materials, do not copy or distribute without written consent . rev.2.0 aug.09, 2010 AX3102 ? package outlines detail a l h e a a2 a1 e d 7 (4x) b y c detail a 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
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