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Optoelectronics/Displays??

Phone market welcomes WLED drivers

Posted: 15 May 2009 ?? ?Print Version ?Bookmark and Share

Keywords:WLED drivers? white LED? feature market phone?

Flash, backlight WLED drivers

Advanced Analogic Technologies Inc. (AnalogicTech) has introduced a set of flash and backlight white LED (WLED) drivers for the feature phone market. Claimed to be offering better efficiencies in power usage in compact packages, the AAT3176 flash driver and the AAT3351 WLED driver help handset designers extend battery life and reduce product footprint.

Operating from a 2.7V to 5.5V input voltage, the AAT3176 flash driver IC supplies up to 500mA output current. The dual mode charge pump maximizes power efficiency by supporting both 1X and 2X operation, and can be programmed across 16 distinct steps via the company's patented S?Cwire (Simple Serial Control) interface. Claiming the industry's smallest package for a 500mA flash driver IC20 percent smaller than comparable devicesthe device allows designers to build highly compact camera lighting solutions.

To maximize design flexibility and minimize programming time, the flash driver IC uses separate external resistors to set maximum flash and movie-mode current. To protect the integrity of the device, the driver features a thermal management system that includes open and short-circuit protection and automatic soft-start circuitry. A load disconnect feature extends battery life by disconnecting the load during shutdown and reducing quiescent current to less than 1.0?A.

The AAT3351 is a high efficiency charge pump capable of driving up to four WLEDs at up to 30mA each. The dual-mode fractional charge pump automatically switches between 1X and 1.5X modes based on input voltage, LED forward voltage and load current to maximize efficiency. A 1MHz switching frequency helps minimize external component size.

To smooth transitions between brightness levels, the device uses the company's S?Cwire serial digital interface to enable, disable and set current to any of 32 levels. LED current output accuracy is 10 percent and LED current matching is 3 percent. The AAT3351 also adds automatic soft-start circuitry and built-in short-circuit protection.

Both ICs are qualified across the -40C to +85C temperature range. The AAT3176 is available in a 2.2mm x 2.2mm, 10-pin TDFN package, and the AAT3351 comes in either a 14-pin TSOPJW or 12-pin TDFN33 package.

- Jean-Pierre Joosting
Microwave Engineering





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