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1/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 1.4mhz, 1a synchronous step-down converter ? general description AX3513 is a high efficiency monolithic synch ronous buck regulator using a constant frequency, current mode architec ture. the device is available in an adjustable version. supply current with no load is 250ua and drops to <1ua in shutdown. the 2.5v to 6v input voltage range makes AX3513 ideally suited for single li-ion, two to four aa battery-powered applications. 100% duty cycle provides low dr opout operation, extending battery life in portable systems. pwm pulse skipping mode oper ation provides very low output ripple voltage for noise sensitive applications. switch ing frequency is internally set at 1.4mhz, allowing the use of small surf ace mount inductors and capacit ors. the internal synchronous switch increases efficiency and decreases need of an external schottky diode. low output voltages are easily supported with the 0.6v feedback reference voltage. AX3513 is available in small tsot23-5l and tdfn-6l packages. ? features - 2.5v to 6v input voltage range - output voltage from 0.6v to vin - high efficiency: up to 96 % - 1.4mhz constant frequency operation - up to 1a output current - quiescent current: 250ua (typical) - no schottky diode required - 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 - tsot23-5l and tdfn-6l pb-free packages free datasheet http:///
2/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 ? block diagram fb en vin sw gnd 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 AX3513 are tsot23-5l and tdfn -6l; the pin assignment is given by: (top view) en gnd sw vin fb 1 23 4 5 tsot23-5l tdfn-6l (2*2) vin fb sw 1 2 3 4 5 6 en gnd nc gnd name description en enable pin h normal operation l shutdown vin power supply input pin sw switch output pin. connect external inductor here. minimize trace area at this pin to reduce emi. gnd ground pin fb output feedback pin nc no connect. free datasheet http:///
3/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 ? order/marking information order information package type AX3513 packing a : taping x x x bt: tsot23-5l z6: tdfn-6l (2*2) top marking (tsot23-5l) top marking (tdfn-6l) g ww: 01~26(a~z) 27~52(a~z) year: a=2010 1=2011 id code: internal AX3513 6 ywx g ww: 01~26(a~z) 27~52(a~z) year: a=2010 1=2011 id code: internal AX3513z6 7 ywx ? absolute maximum ratings (at t a =25c) characteristics symbol rating unit vin pin voltage v in v ss - 0.3 to v ss + 6.5 v feedback pin voltage v fb v ss - 0.3 to v in + 0.3 v en pin voltage v en v ss - 0.3 to v in + 0.3 v switch pin voltage v sw v ss - 0.3 to v in + 0.3 v peak sw sink and source current i psw 1.4 a power dissipation pd ( t j -t a ) / ja mw storage temperature range t st -40 to +150 c operating temperature range t op -40 to +85 c junction temperature t j +125 c tdfn-6l 25 thermal resistance from junction to case tsot23 jc 110 c/w tdfn-6l 120 thermal resistance from junction to ambient tsot23 ja 250 c/w note: ja is measured with the pcb copper area of approximately 1 in 2 (multi-layer). that need connect to gnd pin or exposed pad (AX3513z6). free datasheet http:///
4/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 ? electrical characteristics (v in = v en =3.6v, t a =25c, unless otherwise specified) characteristics symbol conditions min typ max units input voltage range v in 2.5 - 6 v t a = +25c 0.588 0.600 0.612 feedback voltage v fb -40c t a 85c 0.582 0.600 0.618 v feedback bias current i fb v fb =0.65v - - 30 na quiescent current i ccq v fb =1v - 250 350 ua shutdown supply current i sd v en =0v - 0.1 1 ua switching current limit i limit 1.2 1.4 - a line regulation v out /v out v in = 2.5v to 5.5v - 0.04 0.4 %/v load regulation v out /v out i out = 0.01 to 1a - 0.5 - % oscillation frequency f osc sw pin 1.1 1.4 1.7 mhz r ds(on) of p-ch mosfet r dson v fb = 0v, i out = 0.5a - 0.3 0.4 ? r ds(on) of n-ch mosfet r dson (note 1) - 0.25 0.35 ? v enl - - 0.4 en pin lo g ic input threshold voltage v enh 1.5 - - v en pin input current i en - 0.1 1 ua efficiency effi v in =5v, v out =3.3v, i out =0.5a - 94 - % thermal shutdown t ds - 140 - c thermal shutdown hysteresis t sh - 30 - c note 1: guaranteed by design. free datasheet http:///
5/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 ? application circuit v out = 0.6 * (1+r1/r2) r2 300k c1 4.7u c2 10u v out =1.8v r2=100k~330k l1 2.7uh r1 600k u1 AX3513 vin en gnd sw fb c3 15p v in =2.5v~6v ? function descriptions operation AX3513 is a monolithic switch ing mode step-down dc-dc converte r. it utilizes internal mosfets to achieve high efficiency and c an 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 minimum 1000ma output current at input voltage range from 2.5v 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 transient responses and protection of the internal main switch (p-ch mosfet) and synchronous 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 vo ltage. 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. free datasheet http:///
6/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 ? application information setting the output voltage application circuit item shows the basic application circuit with AX3513 adjustable output version. the external resistor sets the output voltage according to the following equation: ? ? ? ? ? ? + = 2 1 1 6 . 0 r r v v out table 1 resistor select for output voltage setting v out r2 r1 1.2v 300k 300k 1.5v 300k 450k 1.8v 300k 600k 2.5v 150k 470k 3.3v 120k 540k inductor selection for most designs, the AX3513 operates with inductors of 2.2 h to 3.3h. 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 20% of the maximum load current 1000ma, i l =200ma. table 2 inductor select for output voltage setting (v in =3.6v) v out 1.2v 1.5v 1.8v 2.5v inductor 2.7uh 2.7uh 2.7uh 2.2uh part number we-tpc 7440430027 7440430027 7440430027 7440430022 note: part type mh or m (www.we-online.com) free datasheet http:///
7/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 for output voltages above 2.0v, when light-l oad efficiency is important, the minimum recommended inductor is 2.7h. for optimum voltage-positioning load transients, choose an inductor with dc series resistance in the 50m ? to 150m ? range. for higher efficiency at heavy loads (above 200ma), or minimal load regul ation (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 (1000ma+100ma). input capacitor selection the input capacitor reduces the surge cu rrent drawn from t he 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 ar e highly recommended because of their low esr and small temperature coefficient s. a 4.7f ceramic capacitor for most applications is sufficient. output capacitor selection the output capacitor is required to be 10uf to keep the output vo ltage ripple small and to ensure regulation loop stability. the output capacitor must have low impedance at the switching frequency. ceramic capacitors with x5r or x7r dielectrics are recommended due to their low esr and high ripple current. compensation capacitor selection the compensation capacitors for increasing phas e margin provide additional stability. it is required 15pf, please refer to demo board schematic to design. free datasheet http:///
8/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 tsot23-5l layout guide en gnd sw fb vin c1 vin gnd l1 vout c2 r1 r2 sw should be connected to inductor by wide and short trace, keep sensitive components away from this trace c2 AX3513 123 4 5 gnd c2's ground must be as closer to ic's gnd pin as possible vin c1 ' s ground must be as closer to ic's gnd pin as possible c2, r1 and r2 must be as closer to ic's fb pin as possible tdfn-6l layout guide gnd nc 1 2 4 5 6 en sw fb ep 3 vin c1 vin gnd l1 vout c2 r1 r2 sw should be connected to inductor by wide and short trace, keep sensitive components away from this trace c2 gnd c1 and c2's ground must be as closer to ic's gnd pin as possible c2, r1 and r2 must be as closer to ic's fb pin as possible and keep the switching trace away. free datasheet http:///
9/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 ? typical characteristics v in vs. v out 1.16 1.18 1.2 1.22 1.24 2.533.544.555.56 v in (v) v out (v) i out = 300ma v in vs. current limit 1 1.2 1.4 1.6 1.8 2 2.533.544.555.56 v in (v) current limit (a) v out = 1.8v v in vs. i ccq 0 100 200 300 400 500 2.5 3 3.5 4 4.5 5 5.5 6 v in (v) i ccq (ua) fb = 1v 0 0.2 0.4 0.6 0.8 1 2.533.544.555.56 v in (v) v enh / v enl (v) v enh v enl v in vs. en threshold voltage temperature vs. v out 1.16 1.18 1.2 1.22 1.24 -40 -20 0 25 50 85 105 125 temperature v out (v) v in = 3.6v temperature vs.i ccq 0 100 200 300 400 500 -40 -20 0 25 50 85 105 125 temperature i ccq (ua) v in = 3.6v free datasheet http:///
10/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 ? typical characteristics (continues) temperature vs. frequency 0.6 0.9 1.2 1.5 1.8 2.1 -40 -20 0 25 50 85 105 125 temperature frequency (mhz) v in = 3.6v i out = 300ma v out vs. efficiency 0 10 20 30 40 50 60 70 80 90 100 0 10 30 50 100 300 500 800 1000 i out (ma) efficiency (%) v out =1.2v v out =1.8v v out =2.5v v in = 3.3v power-on waveform v out vs. efficiency 0 10 20 30 40 50 60 70 80 90 100 0 10 30 50 100 300 500 800 1000 i out (ma) efficiency (%) v out =1.2v v out =1.8v v out =2.5v v out =3.3v v in = 5v power-on waveform en-on waveform free datasheet http:///
11/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 ? typical characteristics (continues) en-on waveform load transient load transient tsd to release tsd to release free datasheet http:///
12/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 ? package outlines (1) tsot23-5l e1 e e e1 b d a a1 a2 y l1 r l c l2 dimensions in millimeters dimensions in inches symbol min. nom. max. min. nom. max. a 0.75 - 1.0 0.030 - 0.039 a1 0.00 - 0.15 0.000 - 0.004 a2 0.70 0.75 0.85 0.028 0.030 0.034 b 0.35 - 0.51 0.014 - 0.020 c 0.10 - 0.25 0.004 - 0.010 d 2.80 2.90 3.00 0.110 0.114 0.118 e 2.60 2.80 3.00 0.102 0.110 0.118 e1 1.50 1.60 1.70 0.059 0.063 0.067 e 0.95 bsc. 0.037 bsc. e1 1.90 bsc. 0.075 bsc. l 0.37 - - 0.015 - - l1 0.60 ref. 0.024 ref. l2 0.25 bsc. 0.010 bsc. y - - 0.10 - - 0.004 r 0.10 - - 0.004 - - 0 o - 8 o 0 o - 8 o free datasheet http:///
13/13 axelite confidential materials, do not copy or distribute without written consent. rev.1.3 jun.25, 2010 AX3513 (2) tdfn-6l (2*2 0.75mm) e d a a1 a3 d2 e e2 (top view) (bottom view) b pin 1 l seating plane (side view) dimensions in millimeters dimensions in inches symbol 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 0.203 ref. 0.008 ref. b 0.20 0.28 0.35 0.009 0.011 0.013 d 1.95 2.00 2.05 0.077 0.079 0.081 d2 1.35 1.50 1.65 0.055 0.059 0.063 e 1.95 2.00 2.05 0.077 0.079 0.081 e2 0.75 0.90 1.05 0.031 0.035 0.039 e 0.65 bsc. 0.026 bsc. l 0.20 0.30 0.40 0.008 0.012 0.016 free datasheet http:///

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