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WLED driver integrates backlight and flash functions

Santa Clara, Calif.—The AAT2848 from Advanced Analogic Technologies, which includes a new tri-mode charge pump driver IC for white LED (WLED) backlight display and flash applications, integrates four backlight channels capable of driving up to 30 mA each, and two camera flash channels capable of driving up to 300 mA each (or 600 mA in parallel). It's all in a 3-by-3 mm TQFN33-20 package that's a viable space-saving solution for mid-range camera phone designers.

“Until recently designers building mid-range camera phones featuring cameras with 2- to 5-megapixel resolution needed to use independent devices for backlight and flash functions,” said Phil Dewsbury, product line manager. “By integrating into a single compact IC both the backlight function and flash output current levels one would expect only from a discrete flash driver IC, the AAT2848 helps handset designers reduce board space, minimize component count and simplify their design.”

New fade-in/fade-out function
The driver IC also features a fade-in/fade-out function, which gradually increases backlight LED brightness from off to fully on across a 63-step linear progression. Fade time is controllable by an external capacitor. This feature, replacing microprocessor-based software schemes, offers a smoother transition to full brightness while reducing software overhead.

The AAT2848 drives the four backlight LED channels in dual mode (1x and 1.5x) operation and its two flash LED channels in tri-mode (1x, 1.5x and 2x). Its Simple Serial Control (S2 C wire) serial digital interfaces set LED current as well as enable and disable the LEDs. For backlight functions the device can set current to any of 32 programmable levels. The flash LED outputs can be set independently across 16 programmable levels. External resistors independently set full-scale current for backlight and flash.

The device also includes a user-programmable safety timer to protect the flash LEDs from thermal damage. This function can be used to terminate a flash event after a pre-determined period. Both the safety timer and flash/strobe operation is enabled via a separate flash-enable pin.

The AAT2848 also comes with integrated short-circuit and over-temperature protection. Soft-start circuitry prevents excessive inrush current at start-up and during mode transitions.

Datasheet: Click here.

Price and availability: The AAT2848, rated for operation over -40 to +85°C, is available in its Pb-free package for $1.42 each in 1k quantities.

AnalogicTech , 1-408-737-4600, www.analogictech.com

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