Bright transitions
07 July 2009
Flash and backlight driver ICs smooth transitions between brightness levels for phones.
Offering new efficiencies in power usage in highly compact packages, AnalogicTech has introduced a set of flash and backlight White LED (WLED) drivers for the highly competitive feature phone market. The AAT3176 flash driver and the AAT3351 WLED driver help handset designers extend battery life and reduce product footprint.
Operating from a 2.7 V to 5.5 V input voltage, the AAT3176 flash driver IC supplies up to 500 mA output current. The dual mode charge pump maximises power efficiency by supporting both 1x and 2x operation and can be programmed across 16 distinct steps via AnalogicTech’s patented S2Cwire (Simple Serial Control) interface. Delivered in the industry’s smallest package for a 500 mA flash driver IC 20% smaller than comparable devices the AAT3176 allows designers to build camera lighting solutions.
The AAT3176 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 μA.
The AAT3351 is a high efficiency charge pump capable of driving up to four White LEDs at up to 30 mA 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 maximise efficiency. A 1 MHz switching frequency helps minimise external component size.
To smooth transitions between brightness levels, the device uses AnalogicTech’s S2Cwire serial digital interface to enable, disable and set current to any of 32 levels. LED current output accuracy is +/-10% and LED current matching is 3%. The AAT3351 also adds automatic soft-start circuitry and built-in short-circuit protection.
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