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Optoelectronics/Displays??

Charge-pump for LED backlights touts 1 percent accuracy

Posted: 23 Jun 2004 ?? ?Print Version ?Bookmark and Share

Keywords:analog devices? adm8845? charge pump?

Analog Devices says its ADM8845 charge pump, which has individual current-control blocks for six white LEDs, achieves the most accurate current-matching in the industry - to within 1 percent for uniformly backlighting the micro color TFT-LCDs used in cell phones, PDAs, and digital cameras.

Two control inputs allow the LEDs to be switched on and off in two independent blocks (four LEDs, and two LEDs), suiting the ADM8845 for the latest clam-shell style mobile phones that feature both a main display and a smaller secondary display. LED brightness can be adjusted by varying the input signal to these control pins.

The charge pump automatically switches between 1x, 1.5x and 2x modes, depending on input voltage from the battery, to maximize power efficiency (up to 88 percent). Soft-start circuitry limits the inrush current to prevent an abrupt start-up. Samples of the ADM8845, in a 16-pin, 3-by-3mm lead frame chip scale package (LFCSP) designed to occupy less than half the space of competing devices, are available now. Production quantities will be available in July 2004. The ADM8845 is priced at 70 cents each in 10k quantities.

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