1/8 ax elite confidential materials, do not copy or distribute without written consent . rev.1.4 aug.18 2010 ax31 16 pwm control 5a step-down converter ? general description ax31 16 consists of step-down switching regul ator with pwm control. these devise include a reference voltage source, oscillation circuit, error amplifier, internal pmos and etc. AX3116 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 protect function and short circui t protect function are built inside, and when ocp or scp happens, the 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 power 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 devices when coupled with the sop-8l-ep 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. ? fea tures - input voltage 4.5v to 23v - output voltage 0.8v to v cc - duty ratio 0% to 100% p wm control - oscillation frequency 330khz typ. - current limit (cl), enable function. - external soft-start function. - thermal shutdown function. - short circuit protect (scp). - built-in internal sw p-channel mos. - sop-8l with exposed pad 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.1.4 aug.18 2010 AX3116 ? block diagram pvcc oscillator circuit reference voltage pwm switched control circuit + - vss v en en ss fb thermal shutdown sw current limit 4ua vcc 110ua ocset ? pin assignmet the package of AX3116 is sop-8l-ep; the 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) ss soft-start pin vcc ic power supply pin pvcc driver power supply pin sw switch pin. connect external inductor/diode here. vss gnd pin ocset add an external resistor to set max switch output current. ? order/marking information order information top marking package type es: sop-8l-ep AX3116 x xx 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 16 ywwx 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.1.4 aug.18 2010 AX3116 ? absolute maximum ratings (at t a =25c) characteristics s y mbol ratin g 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 t opj -20 to +125 c junction temperature ran g e tj -40 to +150 c operatin g suppl y volta g e v op +4.5 to +23 v switchin g current i sw 6.5 a thermal resistance from junction to case jc 15 c / w thermal resistance from junction to ambient ja 40 c / w note :e ja is measured with the pcb copper area(need connect to exposed pad) 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 0.784 0.800 0.816 v quiescent current i ccq v fb =1.2v force driver off - 3 5 ma feedback bias current i fb i out =0.2a - 0.1 0.5 ua shutdown supply current i sd v en =0v - 2 10 ua line regulation v out /v out v cc =8v~23v, i out =0.3a - 1 2 % load regulation v out /v out i out = 0.1 to 2.5a - 0.2 0.5 % ocset pin bias current i ocset 95 110 140 ua ss pin current i ss - 4.0 - ua oscillation frequency f osc sw pin 260 330 400 khz short circuit frequency f osc1 v fb =0v - 80 - 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 d f son v cc =5v, v fb =0v - 70 100 m ? v cc =12v, v fb =0v - 45 70 efficiency effi v out = 5v i out = 3a - 92 - % i out = 5a - 91 - thermal shutdown temp t sd - 135 - 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.1.4 aug.18 2010 AX3116 ? application circuit c2 470uf c4 470uf 12 l1 15uh r5 4.7k r6 1.5k vin+12v vout = 3.3v/5a d1 b540a c5 0.1uf fb 3 en 2 vcc 1 pvcc 7 5 sw 8 vss 6 4 AX3116 c3 0.1uf c6 10nf ss ocset c7 r3 4r7 r1 100k 47nf r2 2k c1 0.1uf l1 recommend value (v in =12v ,i out =5a) v out 1.8 v 2.5v 3.3v 5v l1 10uh 10uh 15uh 15uh ? function descriptions pwm control the AX3116 consists of dc/dc converters that employ a pulse-width modulation (pwm) system. in converters of the AX3116, 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 because the switching frequency remains constant. therefore, these converters provide a low-ripple power over broad r anges of input voltage and load current. setting the output voltage application circuit item shows the basi c application circuit with adjustable output version. the external resistor sets the out put voltage according to the following equation: 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.1.4 aug.18 2010 AX3116 ? ? ? ? ? ? ??? 6 5 10.8 r r v v out table 1 resistor select for output voltage setting v out r6 r5 5v 1.3k 6.8k 3.3v 1.5k 4.7k 2.5v 2.2k 4.7k 1.8v 2k 2.5k 1.5v 2.2k 2.0k 1.2v 3k 1.5k 1.0v 3k 0.75k rds (on) current limiting the current limit threshold is setting by t he external resistor (r2) connecting from v cc supply to ocset pin. the internal 110ua sink current crossing the resi stor sets the voltage at pin of ocset. when the pwm voltage is less than the voltage at ocset, an over-current condition is triggered. please refe r to the formula for se tting the current limit value: r i i ds(on) ocset sw(min) 050r2 . ?? ? (normally, the i sw(max) setting more than i out 1.0a .) example: i sw = (110u x 2k + 0.05)/ 45m= 6.67a (v in =12v) i sw = (110u x 3.75k + 0.05)/ 70m= 6.6a (v in =5v) inductor selection for most designs, the operating inductor range is 10h to 15h. the inductor value can be derived from the following equation: ? ? f i v vvv l osc l in out in out ?? ?? ? ? (t a =25c) 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.1.4 aug.18 2010 AX3116 where is inductor ripple current. lar ge value inductors lower ripple current and small value inductors result in high rippl e currents. choose inductor ripple current approximately 15% of the maximum load current 5a, i l =0.75a. 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 (5a+0.38a) input capacitor the input current to the step-down converter is discontinuous, and so a capacitor is required to supply the ac current to the st ep-down converter while maintaining the dc input voltage. a low-esr capacitor is required to keep the noise at the ic to a minimum. the low-esr electrolytic capacitor may also suffice. the input capacitor value should be greater than 470f. however since it absorbs the input switching current it requires an adequate ripple current rating. its rms current rating should be greater than approximately 1/2 of the dc load current. for insuring stable operation cin should be placed as close to the ic as possible. alternately a smalle r high quality ceramic 0.1uf capacitor may be placed closer to the ic and a lar ger capacitor placed further away . if using this technique, it is recommended that the larger capac itor be a electrolytic type. output capacitor the output capacitor is required to maintain the dc output voltage. low esr capacitors are preferred to k eep the output voltage ripple low. the characteristics of the output capacitor also affect the stability of the regulation control system. the low-esr electrolytic capacitors are recommended. the output capacitor value should be greater than 470f. 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.1.4 aug.18 2010 AX3116 ? typical characteristics 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 4.5510152025 vin vs quiescent current quiescent current (ma) vin (v) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 4.551015202325 vin vs standby current standby current (ua) vin (v) 0.75 0.76 0.77 0.78 0.79 0.8 0.81 0.82 0.83 0.84 0.85 -40 -25 0 25 50 75 100 temperaure vs vfb feedback voltage (v) temperaure () 50 60 70 80 90 100 0.511.522.533.544.55 iout (a) efficiency (%) iout vs efficiency vin=12v vout=3.3v vout=5v power-on load-on transient 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.1.4 aug.18 2010 AX3116 ? package outlines detail a l h e a a2 a1 e d 7 (4x) b y c detail a y x expose pad symbol dimensions in millimeters dimensions in inches min. nom. max. min. nom. max. a - - 1.75 - - 0.069 a 1 0 - 0.15 0 - 0.06 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 x - 2.34 - - 0.092 - y - 2.34 - - 0.092 - 0 o - 8 o 0 o - 8 o mold flash shall not exceed 0.25mm per side jedec outline: ms-012 ba v?mw`r?y?b? w w w . g o f o t e c h . c o m
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