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Multistring white LED driver has 91% efficiency

Posted: 25 Sep 2007 ?? ?Print Version ?Bookmark and Share

Keywords:multistring white LED drivers? WLEDs? power switch?

Semtech Corp. has released two integrated, multistring white LED drivers, the SC440 and SC441, that give notebook and LCD panel manufacturers a high efficiency solution for powering display backlight applications.

The SC440 can power up to six strings of 30mA white LEDs in series and is suitable for notebook computer and other displays that measure up to 15-inches. The SC441 powers up to four strings of 150mA white LEDs in series and is designed for smaller and brighter display applications such as automobile navigation screens or others measuring up to about 9-inches.

The white LED drivers feature 91 percent efficiency at maximum load for improved thermal conditions and longer battery life in portable applications. Screen brightness is kept uniform through an active current matching capability that delivers an industry best 1 percent (typical) current variation across all strings.

The SC440 and SC441 feature a wide 4.5V to 21V input range to meet voltage levels of portable devices. Both devices also offer a pulse-width modulation (PWM) dimming control with frequencies up to 50kHz to deliver a linear brightness range of 0.2 percent to 100 percent.

The highly integrated devices both feature a built-in 2.5A power switch and extensive protection mechanisms. The LED open/short circuit detection disables an LED string with an open or short condition without impacting the other strings. The devices also protect the IC from damage caused by overthermal, overvoltage and overcurrent conditions.

The SC440 is housed in a 4mm x 4mm MLPQ-24 (QFN-24) and the SC441 is available in a TSSOP20. Both packages feature an exposed thermal pad to allow for high-temperature and high-power applications. The devices are lead free and WEEE/RoHS compliant.

Both the SC440 (SC440MLTRT) and SC441 (SC441TETRT) devices are priced at $2.13 each in quantities of 1,000. The devices are available immediately in production quantities.

- Gina Roos

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