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Drivers trim footprint of mid-range camera phones

Posted: 13 Jun 2008 ?? ?Print Version ?Bookmark and Share

Keywords:trimode charge pump driver? white LED? WLED backlight?


Advanced Analogic Technologies Inc. (AnalogicTech) has unveiled the AAT2848, a trimode charge pump driver IC for white LED (WLED) backlight display and flash applications. By integrating four backlight channels capable of driving up to 30mA each with two flash channels capable of driving up to 300mA each, or 600mA in parallel, in a small 3mm x 3mmTQFN33-20 package, this device offers mid-range camera phone designers a highly attractive space-saving solution.

"Until recently designers building mid-range camera phones featuring cameras with 2-5Mpixel resolution needed to use independent devices for backlight and flash functions," said Phil Dewsbury, product line manager at AnalogicTech. "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."

Fade-in/out function
The AAT2848 is a tri-mode charge pump offering 1x, 1.5x and 2x operation. The IC drives four backlight LED channels at up to 30mA each using the charge pump in dual mode (1x and 1.5x) and two flash LED channels at up to 300mA each in tri-mode (1x, 1.5x and 2x).

To enable, disable and set LED current, the AAT2848 features two of AnalogicTech's patented Simple Serial Control serial digital interfaces. 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. Full-scale current is independently set for backlight and flash using external resistors.

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. By replacing microprocessor-based software schemes for the same function, this feature offers a smoother transition to full brightness while reducing software overhead.

The device also adds 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 overtemperature protection. Soft start circuitry prevents excessive inrush current at start-up and during mode transitions.

Qualified across the -40C to 85C temperature range, the AAT2848 is available in a Pb-free, 20-pin TQFN package. The device sells for $1.42 in 1,000 quantities.

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