SC441A

SC441A POWER MANAGEMENT Features „ „ „ „ „ „ „ „ „ „ „ „ „ „ „ „ High Efficiency Integrated Driver for 4-Strings of 150mA LEDs Description The SC441A is a high-efficiency multiple string WLED driver with an integrated boost converter. It operates over a wide input range from 4.5V to 21V with a maximum output voltage of 36V and a 3.0A 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 matching is 2% typical, 3% maximum. The overall efficiency 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 700KHz switching frequency enables the user to optimize the external component sizes for efficiency. When there are fewer than 10 LEDs in each string, users can adjust the output voltage protection yielding an allowable reduction in associated costs, size and voltage ratings of the output capacitor. The SC441A also features comprehensive open and shortcircuit LED protection functions. It disables the corresponding strings with LED open or LED short conditions while maintaining normal operation of other, unaffected LED strings. This feature allows LCD panels to remain viewable even under LED failure, wire disconnect, or short-circuit conditions. The internal thermal shutdown protects the IC from overheating at abnormal conditions. The SC441A is available in a thermally-enhanced TSSOP20 EDP package. Wide input voltage range from 4.5V to 21V 36V maximum output voltage Drives up to 40 WLEDs in 4 strings Programmable LED current for up to 150mA per string +/- 2% string-to-string current matching Up to 90% efficiency Wide 0.2% to 100% PWM dimming range Possible analog dimming Integrated 3.0A power switch 700KHz switching frequency for small size Adjustable OVP for cost-effective output cap selection Open/short LED protection Thermal protection with auto-recovery Thermally enhanced TSSOP-20 EDP package Fully WEEE and RoHS compliant AEC-Q100 Grade 3 qualified Applications Medium-sized LCD panel Notebook Display „ Automotive Car Navigation Display „ Sub-Notebook and Tablet Computer Displays „ Portable Media Players „ „ Typical Application Circuit Vin (4.5V -21V) 1 2 VIN EN FFLAG PWM OVPRTN SW SW VOUT OVPIN OVPIN 4 Strings SC441A COMP IO1-4 IO1- 4 IOSET IOSET AGND AGND 4 10 SS EDP PGND PGND IOGND PGND January 18, 2010 www.semtech.com 1