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1/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b 1.2mhz, 2a synchronous step-down converter ? general description the ax3514/a/b is a 1.2mhz constant frequency current mode pwm step-down converter. it is ideal for portable equipment requiring very high current up to 2a from single-cell lithium-ion batteries while still ac hieving over 90% efficiency during peak load conditions. the ax3514/a/b also can run at 100% duty cycle for low dropout operation, extending battery life in portable systems while light load operation prov ides very low output ripple for noise sensitive applications. the ax3514/a/b can supply up to 2a output load current from a 2.6v to 5.5v input voltage and the output volt age can be regulated as low as 0.6v. the high switching frequency minimizes the size of external components while keeping switching losses low. the internal sl ope compensation setting allows the device to operate with smaller inductor values to optim ize size and provide efficient operation. the ax3514/a/b is available in adjustable (0.6v to vin) output voltage. the device is available in sop-8l pb-free and td fn-10l packages. ? features - 2.6v to 5.5v input voltage range - output voltages from 0.6v to vin - high efficiency: up to 96 % - 1.2mhz constant frequency operation - up to 2a output current - no schottky diode required - low r ds(on) internal switches: 0.15 ? - current mode operation for excell ent line and load transient response - current limit, enable function - short circuit protect (scp) - build-in soft start function - 1a shutdown current - sop-8l pb-free and tdfn-10l packages
2/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b ? block diagram fb en sgnd svin pvin lx pgnd over-temperature and short-circuit protection ref soft-star 0.6v + - - + icomp - + isense amp osc slope comp pwm logic - + izero comp non-overlap control reset set enable logic ? pin assignment the packages of ax3514/a/b are sop-8l and td fn-10l; the pin assignment is given by: tdfn-10l (3*3) en ax8101/a lx 1 fb 10 2 3 4 5 6 7 8 9 pvin svin sgnd sgnd lx pgnd pgnd ax3514 (gnd) ax3514a ( top view ) 1 2 3 4 8 7 6 5 svin sgnd sop-8l fb nc pgnd lx pvin en
3/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b name description en enable pin h normal operation l shutdown pvin power supply input pin svin signal supply input pin lx switch output pin. connect external inductor here. minimize trace area at this pin to reduce emi. sgnd signal ground pin pgnd power ground pin fb output feedback pin nc no connect pin ? order/marking information order information blank : taping package type s: sop-8l ax3514 packing j10: tdfn-10l (3*3) xxx x x pin define blank: ax3514 a: ax3514 (sop-8l only) b: ax3514 (sop-8l only) a : taping top marking (sop-8l) top marking (tdfn-10l) ax logo part number id code: internal ww: 01~52 year: 10=2010 11=2011 blank:ax3514 a : ax3514a (sop8 only) b : AX3514B (sop8 only) 351 4 y y w wx x part number id code: internal ww: 01~52 year: 10=2010 11=2011 351 4 y y w wx
4/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b ? absolute maximum ratings (at t a =25c) characteristics s y mbol ratin g unit pvin, svin pin volta g e v in v ss - 0.3 to v ss + 6 v feedback pin volta g e v fb v ss - 0.3 to v in + 0.3 v en pin volta g e v en v ss - 0.3 to v in + 0.3 v switch pin volta g e v lx v ss - 0.3 to v in + 0.3 v power dissipation pd ( t j -t a ) / ja mw stora g e temperature ran g e t st -40 to +150 c operatin g temperature ran g e t op -40 to +85 c junction temperature t j +125 c thermal resistance from junction to case sop-8l jc 40 c/w tdfn-10l 15 thermal resistance from junction to ambient sop-8l ja 120 c/w tdfn-10l 45 note: ja is measured with the pcb copper area of approximately 1 in 2 (multi-layer). that need connect to lx pin or exposed pad of the ax3514. ? electrical characteristics (v in = v en =3.6v, t a =25c, unless otherwise specified) characteristics symbol conditions min typ max units supply voltage range v in 2.6 - 5.5 v feedback voltage v fb t a = +25c 0.5880 0.6000 0.6120 v t a = 0c t a 85c 0.5865 0.6000 0.6135 t a = -40c t a 85c 0.5820 0.6000 0.6180 feedback bias current i fb v fb =0.65v - - 30 na quiescent current i ccq v fb =0.8v - 250 400 ua shutdown supply current i sd v en =0v - 0.1 1 ua switching current limit i limit 2.2 2.5 - a line regulation v out /v out v in = 2.6v~5.5v - 0.04 0.4 %/v load regulation v out /v out i out = 0.01 to 2a - 0.5 1 % oscillation frequency f osc lx pin 1 1.2 1.4 mhz r ds ( on ) of p-ch mosfet r dson v fb =0v, i out =1a - 0.15 0.25 ? r ds ( on ) of n-ch mosfet r dson (note1) - 0.11 0.20 ? en pin lo g ic input threshold voltage v enl - - 0.4 v v enh 1.5 - - en pin input current i en - 0.1 1 ua efficiency effi v in =5v, v out =3.3v,i out =1.5a - 91 - % thermal shutdown t sd - 140 - c thermal shutdown hysteresis t sh - 30 - c note1: guaranteed by design.
5/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b ? application circuit v out = 0.6 * (1+r2/r3) r3 300k c1 22uf c2 22uf v out =1.8v v in =2.6 to 5.5v r2=510k~820k l1 3.3uh r2 600k u1 ax3514 pvin en sgnd lx fb c5 15pf svin pgnd r1 10r c3 100nf ? function descriptions operation ax3514/a/b is a monolithic switching mode step-down dc- dc converter. it utilizes internal mosfets to achieve high efficien cy and can generate very low output voltage by using internal reference at 0.6v. it operates at a fixed switching frequency, and uses the slope compensated current mode architecture. this step-down dc-dc converter supplies 2000ma output current at input vo ltage range from 2.6v to 5.5v. current mode pwm control slope compensated current mode pwm cont rol provides stable switching and cycle-by-cycle current limit for excellent load and line responses and protection of the internal main switch (p-ch mosfet) and syn chronous rectifier (n-ch mosfet). during normal operation, the internal p-ch mosfet is turned on for a certain time to ramp the inductor current at each rising edge of the inte rnal oscillator, and switched off when the peak inductor current is above the error voltage. the current comparator, i comp limits the peak inductor current. when the main switch is o ff, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, i zero , or the beginning of the next clock cycle.
6/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b ? application information setting the output voltage application circuit item shows the basic application circuit with ax3514/a/b adjustable output version. the external resistor sets the output voltage according to the following equation: ? ? ? ? ? ? ? ? ? 3 2 1 6 0 r r v v out . table 1: resistor select for output voltage setting v out r3 r2 1.2v 680k 680k 1.5v 420k 630k 1.8v 300k 600k 2.5v 180k 560k 3.3v 150k 680k inductor selection for most designs, the ax3514/a/b operates wi th inductors of 2.2h to 4.7h. low inductance values are physically smaller but require faster swit ching, which results in some efficiency loss. the inductor value can be derived from the following equation: ? ? f i v v v v l osc l in out in out ? ? ? ? ? ? where is inductor ripple cu rrent. large value inductors lo wer ripple current and small value inductors result in high ripple currents. choose inductor ripple current approximately 15% of the maximum load current 2000ma, i l =300ma. table 2 inductor select for output voltage setting (v in =3.6v) v out 1.2v 1.5v 1.8v 2.5v inductor 3.3uh 3.3uh 3.3uh 2.2uh part number we-tpc 744062003 744062003 744062003 744043022 note: part type l (www.we-online.com) for output voltages above 2.0v, when light-l oad efficiency is important, the minimum recommended inductor is 2.2h. for optimum vo ltage-positioning l oad transients, choose an inductor with dc series resistance in the 30m ? to 100m ? range. for higher efficiency at heavy loads (above 200ma), or minimal load regulat ion (but some transient overshoot), the resistance should be kept below 100m ? . 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 (2000ma+350ma).
7/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b input capacitor selection the input capacitor reduces the surge cu rrent drawn from the input and switching noise from the device. the input capacitor impedance at the switching frequency shall be less than input source impedance to prevent hi gh frequency switching current passing to the input. a low esr input capacitor sized for maximum rms current must be used. ceramic capacitors with x5r or x7r dielectrics are highly recomm ended because of their low esr and small temperature coefficients. a 22f ce ramic capacitor for most applications is sufficient. output capacitor selection the output capacitor is required to keep the output voltage rippl e small and to ensure regulation loop stability. the output capacito r must have low impedance at the switching frequency. ceramic capacitors with x5r or x7 r dielectrics are re commended due to their low esr and high ripple current. compensation capacitor selection the compensation capacitor (c5) for improving phase ma rgin provides additional stability. refer to demo board schematic. t he optimum value is 15pf for all conditions. layout guide pvin en sgnd sw fb svin pgnd ax3514 expose pad 8 1 2 3 4 5 6 7 sgnd c1 c3 vin r1 gnd l1 vout c2 r2 r3 c3 must be placed between svin and sgnd as closer as possible sw should be connected to inductor by wide and short trace, keep sensitive components away from this trace c1 must be placed between pvin and pgnd as closer as possible, vin trace should be wide and short. c5
8/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b vin gnd c3 must be placed between svin and sgnd as closer as possible sw should be connected to inductor by wide and short trace, keep sensitive components away from this trace c 1 must be placed betwee n pvin and pgnd as closer as possible, vin trace should be wide and short. en lx 1 fb 10 2 3 4 7 8 9 pvin svin sgnd lx pgnd pgnd ax3514j10 c3 r1 c1 vout l1 exposed pad c2 r3 r2 5 6 vout sgnd c5 fb pvin en sgnd lx fb svin pgnd ax3514a expose pad 8 1 2 3 4 5 6 7 sgnd c1 c3 vin r1 l1 vout c2 r2 r3 c3 must be placed between svin and sgnd as closer as possible sw should be connected to inductor by wide and short trace, keep sensitive components away from this trace c1 must be placed between pvin and pgnd as closer as possible, vin trace should be wide and short. vin c5 gnd r2, r3 and c5 should be connected to fb pin by short trace pvin fb sgnd lx nc svin pgnd AX3514B expose pad 8 1 2 3 4 5 6 7 en c1 c3 vin r1 l1 vout c2 r2 r3 c3 must be placed between svin and sgnd as closer as possible sw should be connected to inductor by wide and short trace, keep sensitive components away from this trace c1 must be placed between pvin and pgnd as closer as possible, vin trace should be wide and short. vin c5 gnd
9/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b ? typical characteristics v out vs. efficiency (v in =3.3) 0 10 20 30 40 50 60 70 80 90 100 0 10 50 100 500 1000 1500 2000 i out (ma) efficiency (%) v out =2.5v v out =1.8v v out =1.2v v out vs efficiency (v in =5v) 0 10 20 30 40 50 60 70 80 90 100 0 10 50 100 500 1000 1500 2000 i out (ma) efficiency (%) v out =3.3v v out =2.5v v out =1.8v v out =1.2v load rrgulation 1.18 1.185 1.19 1.195 1.2 1.205 1.21 1.215 1.22 0 500 1000 1500 2000 2500 i out (ma) v out (v) v in =3.6v line regulation 1.18 1.185 1.19 1.195 1.2 1.205 1.21 1.215 1.22 2.533.544.555.5 v in (v) v out (v) i out =500ma v in vs. frequency 1.1 1.12 1.14 1.16 1.18 1.2 1.22 1.24 1.26 1.28 1.3 1.32 1.34 2.5 3 3.5 4 4.5 5 5.5 v in (v) frequency (mhz) v in vs. i ccq 100 150 200 250 300 350 400 2.53 3.544.555.5 v in (v) i ccq (ua) v fb =0.8v
10/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b ? typical characteristics (continuous) temperature vs. v out 1.1 1.12 1.14 1.16 1.18 1.2 1.22 1.24 1.26 1.28 1.3 1.32 1.34 -40 -20 0 25 50 85 105 125 temperature v out (v) v in =3.6v i out =10ma temperature vs. i ccq 0 50 100 150 200 250 300 350 400 -40 -20 0 25 50 85 105 125 temperature i ccq (ua) v fb =0.8v v in =3.6v rds (on) vs. v in 80 100 120 140 160 180 200 220 2.5 3 3.5 4 4.5 5 v in (v) p-mos n-mos i out =1a rds (on) m ? temperature vs. frequency 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40 1.45 1.50 -40 -20 0 25 50 85 105 125 frequency (mhz) temperature power on v in =5v, v out =1.2v, load=1a load transient response v in =5v, v out =1.2v, i out = 0.2a~1.8a
11/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b ? package outlines (1) sop-8l h e a a2 a1 c 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
12/12 axelite confidential materials, do not copy or distribute without written consent . rev.1.8 nov.09, 2011 a x3514 / a / b (2) tdfn-10l (3*3*0.75mm) symbol dimensions in millimeters dimensions in inches min. nom. max. min. nom. max. a 0.70 0.75 0.80 0.028 0.030 0.031 a1 0.00 0.02 0.05 0.000 0.001 0.002 a3 0.20 ref. 0.008 ref. b 0.18 0.25 0.30 0.007 0.010 0.012 d 2.90 3.00 3.10 0.114 0.118 0.122 d2 2.20 2.40 2.50 0.087 0.094 0.098 e 2.90 3.00 3.10 0.114 0.118 0.122 e2 1.50 1.60 1.70 0.059 0.063 0.070 e 0.50 bsc. 0.020 bsc. l 0.30 0.40 0.50 0.012 0.016 0.020

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