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Charge pumps enable smaller, feature-rich handsets

Posted: 13 Aug 2007 ?? ?Print Version ?Bookmark and Share

Keywords:charge pumps? smaller phones? feature-rich handsets?

AnalogicTech has introduced two charge pump products designed to enable designers to build smaller, more feature-rich mobile handsets. The AAT2846 and AAT2856 combine backlight drivers, high-current flash drivers and two general-purpose LDOs linear regulators in a single 4mm x 4mm package.

The devices also maximize design flexibility by offering independent control for backlight and flash current drive via separate single-wire digital interfaces.

As today?s high-performance handsets and other portable devices rapidly evolve and add new features, their lighting functions are growing increasingly complex. Many now require WLEDs for backlight of large and sophisticated main displays, WLEDs for backlight of smaller sub displays, and flash LEDs for camera functions. By combining six outputs for WLEDs, two for flash and two LDOs on the same chip, and providing independent control for each function, the AAT2846 and AAT2856 offer portable system designers the opportunity to build dramatically smaller and more economical portable systems.

The AAT2846 uses a high current, tri-mode charge pump capable of driving up to six backlight LEDs at 30mA each and two flash LEDs at up to a total of 600mA. For applications that do not require flash functionality, the AAT2856 offers a high current tri-mode charge pump designed to drive six backlight LEDs at up to 30mA each.

Both devices feature AnalogicTech?s AS?Cwire single-wire interface to independently enable, disable and set drive current for backlight and flash LEDs. Current for backlight LEDs on the AAT2846 and AAT2856 can be programmed to any of 32 levels ranging from 95?A to 30mA. The devices also provide a 20mA full-scale range and a special low-current address for optimal performance at low LED current levels. The six backlight outputs can also be segmented into a 5 + 1 configuration to support dual-panel mobile handset applications.

The AAT2846 and AAT2856 also feature integrated short-circuit and overtemperature protection. Soft start circuitry automatically prevents excessive inrush current at start up and mode transitions.

Both devices are qualified across the -40C to 85C temperature range. The AAT2846 comes in a Pb-free, 28-lead TQFN44 package, and the AAT2856 is available in a Pb-free TQFN44-28 package.

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