WLED drivers from AnalogicTech

AnalogicTech has introduced 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 3mm TQFN33-20 package, the 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 to 5 megapixel resolution needed to use independent devices for backlight and flash functions. 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, minimise component count and simplify their design.

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 (S2Cwire) 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 an innovative fade-in/fade-out function that 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 of time. 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.

Qualified across the -40 C to +85 degree C temperature range, the AAT2848 is available in a Pb-free, 20-pin TQFN package.

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