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WLED drivers backlight entry-level phone displays

Posted: 19 May 2008 ?? ?Print Version ?Bookmark and Share

Keywords:WLED drivers? backlight displays? entry-level cellphones?

Advanced Analogic Technologies Inc. (AnalogicTech) has rolled out the AAT3103, constant frequency, charge-pump-based, current source white LED (WLED) drivers. Designed to backlight lower-cost LCD displays in entry-level and reduced feature set cellphones, the two devices help reduce system costs by using a small 2mm x 2.1mm package while requiring only two external components.

"Most entry-level cellphones targeted at today's rapidly growing emerging markets typically offer very basic lighting features including a small monochrome TFT-LCD panel and minimal accessory lighting," says Phil Dewsbury, product line director for AnalogicTech. "The new current-sourced AAT3103 deliver up to 30mA per channel to allow designers to cost-effectively build systems that provide high readability with these low cost panels, while keeping system costs low by using small packages and a minimal number of external components."

Charge pumps
Both new WLED drivers are current-sourced devices designed for applications where an LED cathode is connected to ground. To ensure high readability in lower-cost, more opaque LCD panels, the AAT3103 drives up to three LEDs at up to 30mA each. The charge pumps in each driver automatically switch between 1X and 2X mode to maintain high efficiency. Both new WLED drivers offer current accuracy of better than 10 percent. Channel-to-channel current matching exceeds 3 percent.

LEDs can be programmed using either a traditional PWM-compatible interface, up to 50kHz or via AnalogicTech's proprietary single-wire S2Cwire interface. Using the S2Cwire interface, designers can program each WLED over 16 or 8 steps.

To keep solution size small and affordable, the new drivers only require two external devices: a 1?F capacitor for the charge pump and an external resistor to set full-scale LED current.

The AAT3103 also offer a low-shutdown current feature which disconnects the load from IN and reduces quiescent current to Both devices are qualified across the -40&176;C to 85C temperature range and come in a compact 2mm x 2.1mm SC70JW-10 package. The AAT3103 sells for 52 cents in 1,000 quantities.

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