highfefciencyfintegratedfdriverfforf 4-stringsfoff150mafleds sc441 powerfmanagement september 28, 2010 1 www.semtech.com not recommended for new designs: see sc441a features applications description ? wide input voltage range from 4.5v to 21v ? 36v maximum output voltage ? drives up to 40 wleds in 4 strings f ? programmablef ledf currentf forf upf tof 150maf perf stringf f ? +/-f2%fstring-to-stringfcurrentfmatching f ? upftof90%ffefciency ? wide 0.2% to 100% pwm dimming range ? possible analog dimming ? integrated 2.5a power switch ? 800khz switching frequency for small size ? adjustable ovp for cost-efective output cap selection f ? open/shortfledfprotection ? thermal protection with auto-recovery ? thermally enhanced tssop-20 edp package ? fully weee and rohs compliant ? medium-sized lcd panel ? notebook display ? automotive car navigation display ? sub-notebook and tablet computer displays ? portable media players the sc441 is a high-efciency multiple string wled driver with an integrated boost converter. it operates over a wide input range from 4.5v to 21v with a maximum out - put voltage of 36v and a 2.5a internal power switch. it can drive up to forty wleds in 4 strings with current up to 150ma per string. the string-to-string current match - ing is 2% typical, 3% maximum. the overall efciency is greater than 90% due to the low current sense voltage and a low-impedance internal power switch. the wide pwm dimming range boasts a ratio of 500: 1. the 800khz switching frequency enables the user to op - timize the external component sizes for efciency. when there are fewer than 10 leds in each string, users can ad - just the output voltage protection yielding an allowable reduction in associated costs, size and voltage ratings of the output capacitor. the sc441 also features comprehensive open and short- circuit led protection functions. it disables the corre - sponding strings with led open or led short conditions while maintaining normal operation of other, unafected led strings. this feature allows lcd panels to remain view - able even under led failure, wire disconnect, or short-cir - cuit conditions. the internal thermal shutdown protects the ic from overheating at abnormal conditions. the sc441 is available in a thermally-enhanced tssop-20 edp package. typicalfapplicationfcircuit 1 4 vout ss pgnd ioset io1-4 comp ovpin agnd vin sw pwm en ovprtn sw fflag pgnd iognd sc441 4 strings 1 10 vin (4.5v -21v) 2 edp pgnd ioset io1- 4 comp ss agnd vout ovpin not recommended for new designs
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