fremont micro devices FT441 www.fremontmicro.com page 1 of 10 ds441-a2 1.5mhz, 900ma synchronous step-down converter features ? high efficiency - up to 95% ? guaranteed 900ma output current ? 2.5v to 5.5v input voltage range ? 1.5mhz constant frequency operation ? no external scho ttky diode needed ? adjustable output voltages from 0.6v to vin ? fixed output voltage options available ? 100% duty cycle low-dropout operation ? 0.1 a shutdown current ? sot23-5 package typical applications ? cellular phones ? dsp core supplies ? xdsl applications ? usb powered modems ? digital still cameras ? portable instruments ? pc cards and notebooks description the FT441 is a 1.5mhz constant frequency, slope compensated current mode step down converter. it is ideal for portable equipment requiring very high current up to 0.9a from single-cell lithium-ion batteries while still achieving over 90% efficiency during peak load conditions. the FT441 integrates a main switch and a synchronous rectifier for high efficiency without an external schottky diode. the FT441 automatically turns off the synchronous rectifier to increase efficiency while enters discontinuous pwm mode. the FT441 can run at 100% duty cycle for low dropout operation, maximizing battery life in portable application. FT441 consumes less than 1ua when enter shutdown mode. the FT441 is available in a fixed output voltages of 1.2v, 1.5v, and 1.8v, and is also available in an adjustable output voltage version capable of generating output voltages from 0.6v to vin .the FT441 is available in a 5-pin sot23-5 package.
fremont micro devices FT441 www.fremontmicro.com page 2 of 10 ds441-a2 typical application circuit vout 1.8v v in en sw v fb gnd 4 2 1 3 5 vin 2.7~4.2v 10uf 2.2uh 100k 200k 22pf 10u f FT441 c1 c2 r1 r2 c3 l1 figure 1: typical application circuit absolute maximum ratings vin to gnd????????????.???????????????????????-0.3v to 6v en to gnd..?????????????????.?????? ??????.. ??-0.3v to (vin+0.3) vfb to gnd..???????????????????????????????. -0.3v to (vin+0.3) sw to gnd???????.???????????????????????.??-0.3v to (vin+0.3) peak sw sink and source current????? ...??????????????????.internally limited junction to ambient thermal resistance ( ja ).????????.??????????????250 /w operating temperature range??????.????????????????????...-40 to +85 junction temperature???????????????????????????..?.... -40 to +150 storage temperature range ??????????..???????????????.?.-55 to +150 lead temperature (soldering, 10sec) ?????????????????????????...?...300 stresses exceeding maximum ratings may damage the device. maximum ratings are stress ratings only. functional operation above the reco mmended operating conditions is not implied. extended exposure to stresses above the recommended operating conditions may affect device reliability .
fremont micro devices FT441 www.fremontmicro.com page 3 of 10 ds441-a2 pin comfiguration figure 2: package top view terminal definition pin name description 1 en enable control input 2 gnd ground 3 sw switching node, connecting to inductor 4 v in power input 5 v fb /v out feedback node. vfb for adjustable version, and vout for fixed output version table 1
fremont micro devices FT441 www.fremontmicro.com page 4 of 10 ds441-a2 ordering information FT441 ? designator symbol output voltage a adj b 1.5v c 1.8v d 2.5v e 1.2v f 2.8v g 3.3v designator symbol package type a sot23-5 table 2 marking rule 12 4 3 5 . ???? figure 3 represent product series symbol product series 1 FT441xx table 3 represent output voltage represent package tape ? for internal reference
fremont micro devices FT441 www.fremontmicro.com page 5 of 10 ds441-a2 block diagram figure 4: FT441 block diagram
fremont micro devices FT441 www.fremontmicro.com page 6 of 10 ds441-a2 electrical characteristics (v in = v en = 3.6v, t a = 25 ? c unless otherwise specified.) parameter symbol test conditions min typ max unit input voltage range v in 2.5 5.5 v under voltage lockout threshold v uvlo v in rising 2.2 2.35 2.5 v operating supply current v fb =0.5 or vout=90% 300 450 ua shutdown supply current v en = 0v, v in = 4.2v 0.1 1 ua t a = 25c 0.588 0.6 0.612 0 < t a < 85c 0.585 0.6 0.615 adjustable version regulation voltage v fb -40c < t a < 85c 0.582 0.6 0.618 FT441ba 1.455 1.5 1.545 FT441ca 1.746 1.8 1.854 FT441da 2.425 2.5 2.575 FT441ea 1.164 1.2 1.236 FT441fa 2.716 2.8 2.884 fixed output regulation voltage v out FT441ga 3.2 3.3 3.4 v output voltage line regulation v in = 2.5v to 5.5v 0.1 0.5 %/v output voltage load regulation i out = 0ma to 900ma 0.5 % inductor current limit i lim v in = 3.6v, v fb =0.5v or vout=90% 1.15 1.5 1.8 a v fb =0.6 or v out =100% 1.2 1.5 1.8 mhz oscillator frequency f sw v fb =0 or v out =0 400 khz pmos on resistance r onp i sw = -100ma 0.28 0.4 ? nmos on resistance r onn i sw = 100ma 0.22 0.35 ? sw leakage current en = 0, v in = 5.5v, v sw = 5.5v or 0v 1 ua en threshold v ih v in = 2.5v to 5.5v 0.3 1 1.5 v en leakage current i en v in = 5.5v, en = v in 0.01 1 ua table 4
fremont micro devices FT441 www.fremontmicro.com page 7 of 10 ds441-a2 typical performance characteristics efficiency vs output current @vout=1.8v 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 output current(ma) efficiency(%) vcc=2.7 vcc=3.6 vcc=4.2 efficiency vs output current @vout=3.3v 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) vcc=3.7 vcc=4.2 vcc=5.0 efficiency vs output current @vout=2.5v 30 40 50 60 70 80 90 100 1 10 100 1000 output current(ma) efficiency(%) vcc=2.7 vcc=3.6 vcc=4.2 vcc=5 efficiency vs output current @vout=1.8v 60 70 80 90 100 23456 output current(ma) efficiency(%) iou t=10ma iou t=200m a iou t=500m a iou t=1a
fremont micro devices FT441 www.fremontmicro.com page 8 of 10 ds441-a2 load regulation @vout=1.8v 1.77 1.775 1.78 1.785 1.79 1 10 100 1000 iout(ma) vout(v) vcc=2.7 vcc=3.6 vcc=4.2 vcc=5
fremont micro devices FT441 www.fremontmicro.com page 9 of 10 ds441-a2 application information figure4 below shows the typical application circuit with FT441 fixed output versions. vin vout 1.8v v in en sw v out gnd 4 2 1 3 5 2.7~4.2v 10uf 2.2 uh 10uf c1 c2 l1 FT441 figure 4 typical application circu it with fixed output versions inductor selection under normal operation, the inductor maintains continuous current to the output. its value is chosen based on the desired ripple current. large value inductors lower ri pple current, and small value inductors result in higher ripple currents. the inductor value can be derived from the following equation: osc l in out in out f i v v v v l ? ? ? ? ? ? ) ( , where S i l is inductor ripple current. input capacitor selection the input capacitor reduces input voltage ripple to the converter; a 10uf ceramic capacitor is recommended for most applications. output capacitor selection the output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. the output capacitor must have low impedance at the switching frequency. the output ripple S vout approximately: ) 8 1 ( out l out fc esr i v ? ? ? ? ? output voltage programming figure1 above shows the typical applicati on with FT4412 adjustable version. the external resistor sets the output voltage according to following equation: ) 1 2 1 ( 6 . 0 r r v v out ? ? ?
fremont micro devices FT441 www.fremontmicro.com page 10 of 10 ds441-a2 sot23-5 package dimensions in millimeters dimensions in inches symbol min max min max a 1.050 1.250 0.041 0.049 a1 0.000 0.100 0.000 0.004 a2 1.050 1.150 0.041 0.045 b 0.300 0.500 0.012 0.020 c 0.100 0.200 0.004 0.008 d 2.820 3.020 0.111 0.119 e 1.500 1.700 0.059 0.067 e1 2.650 2.950 0.104 0.116 e 0.95 (bsc) 0.037 (bsc) e1 1.800 2.000 0.071 0.079 l 0.300 0.600 0.012 0.024 0 8 0 6
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