high eciency integrated driver for 3strings of 100ma leds SC446 power management january 28, 2010 1 www.semtech.com features applications description wide input voltage range from 4.5v to 27v 36v maximum output voltage drives up to 30 wleds in 3 strings programmable led current for up to 100ma per string +/ 2% stringtostring current matching up to 90% eciency wide 0.2% to 100% pwm dimming range possible analog dimming integrated 2.5a power switch 700khz switching frequency for small size adjustable ovp for costeective output cap selecti on open/short led protection thermal protection with autorecovery thermally enhanced tssop16 edp package pb free, halogen free, andweee/rohs compliant mediumsized lcd panel notebook display automotive car navigation display subnotebook and tablet computer displays portable media players the SC446 is a higheciency multiple string wled driver with an integrated boost converter. it operates over a wide input range from 4.5v to 27v with a maximum out put voltage of 36v and a 2.5a internal power switch. it can drive up to thirty wleds in 3 strings with current up to 100ma per string. the stringtostring current match ing is 2% typical, 3% maximum. the overall eciency is greater than 90% due to the low current sense voltage and a lowimpedance internal power switch. the wide pwm dimming range boasts a ratio of 500: 1. the 700khz switching frequency enables the user to op timize the external component sizes for eciency. 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 SC446 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, unaected led strings. this feature allows lcd panels to remain viewable even under led failure, wire disconnect, or shortcircuit conditions. the internal thermal shutdown protects the ic from overheating at abnormal conditions. the SC446 is available in a thermallyenhanced tssop16 edp package. typical application circuit !"#$ %% &'() *"%+$ *",-. /"0& "!&*( 1'() !*( %2 &20 +( %/..3 4%56789: , ,; !784<.=>!4-?@!a ? +)& &'() *"%+$ *",- /"0& %% 1'() !"#$ "!&*( !*( "!&b$(
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