higheciencyintegrateddriverfor 4stringsof150maleds SC441C powermanagement march04,2010 1 www.semtech.com features applications description ? wideinputvoltagerangefrom4.5vto27v ? 42vmaximumoutputvoltage ? drivesupto48wledsin4strings ? programmable led current for up to 150ma per string ? +/2%stringtostringcurrentmatching ? upto90%eciency ? wide0.2%to100%pwmdimmingrange ? possibleanalogdimming ? integrated2.5apowerswitch ? 700khzswitchingfrequencyforsmallsize ? adjustableovpforcosteectiveoutputcapselecti on ? open/shortledprotection ? thermalprotectionwithautorecovery ? thermallyenhancedtssop20edppackage ? pbfree,halogenfree,andweee/rohscompliant ? mediumsizedlcdpanel ? notebookdisplay ? automotivecarnavigationdisplay ? subnotebookandtabletcomputerdisplays ? portablemediaplayers theSC441Cisahigheciencymultiplestringwleddriv er with an integrated boost converter. it operates over a wide input range from 4.5v to 27v with a maximum outputvoltageof42vanda2.5ainternalpowerswitch. itcandriveupto48wledsin4stringswithcurrentup to150maperstring.thestringtostringcurrentmatch ingis2%typical,3%maximum.theoveralleciencyis greater than 90% due to the low current sense voltage and a lowimpedance internal power switch. the wide pwmdimmingrangeboastsaratioof500:1. the700khzswitchingfrequencyenablestheusertoop timizetheexternalcomponentsizesforeciency.when therearefewerthan12ledsineachstring,userscanad justtheoutputvoltageprotectionyieldinganallowable reductioninassociatedcosts,sizeandvoltageratingsof theoutputcapacitor. theSC441Calsofeaturescomprehensiveopenandshort circuit led protection functions. it disables the corre spondingstringswithledopenorledshortconditions whilemaintainingnormaloperationofother,unaected led strings. this feature allows lcd panels to remain viewable even under led failure, wire disconnect, or shortcircuit conditions. the internal thermal shutdown protectstheicfromoverheatingatabnormalconditions. theSC441Cisavailableinathermallyenhancedtssop20 edppackage. typicalapplicationcircuit 9 2 8 7 6 6 3 * 1 ' , 2 6 ( 7 , 2 & 2 0 3 2 9 3 , 1 $ * 1 ' 9 , 1 6 : 3 : 0 ( 1 2 9 3 5 7 1 6 : ) ) / $ * 3 * 1 ' , 2 * 1 ' 6 & & 6 w u l q j v 9 l q 9 9 ( ' 3 3 * 1 ' , 2 6 ( 7 , 2 & 2 0 3 6 6 $ * 1 ' 9 2 8 7 2 9 3 , 1 9 r x w 9
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