原标题：Semtech SC446高效多串WLED驱动方案

　　Semtech公司的SC446是集成了升压转换器的高效多串WLED驱动器,输入电压从4.5V到27V,最大输出电压36V,内部功率开关为2.5A,能驱动3串多达30个WLED,每串电流100mA,串与串的电流匹配典型值为2%,整体效率大于90%,主要用在中型LCD屏,笔记本电脑显示,汽车导航显示和手提媒体播放器.本文主要介绍SC446主要特性和典型应用电路.

　　The SC446 is a high-efficiency 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 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 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 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 SC446 is available in a thermally-enhanced TSSOP-16 EDP package.

　　SC446主要特性:

　　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% string-to-string 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 cost-e!ective output cap selection

　　Open/short LED protection

　　Thermal protection with auto-recovery

　　Thermally enhanced TSSOP-16 EDP package Pb Free, Halogen Free, andWEEE/RoHS Compliant

　　SC446应用:

　　Medium-sized LCD panel

　　Notebook Display

　　Automotive Car Navigation Display

　　Sub-Notebook and Tablet Computer Displays

　　Portable Media Players

　　图1.SC446典型应用电路