Charge Pump Powers Phone-Camera Flashes August 2004 Issue Published Date: August 12, 2004
Intended to power the flash function in cellular phones, the AAT3112 is a dual charge-pump voltage doubler capable of delivering 500 mA of pulsed current to white and RGB LEDs that perform the flash function. The charge pump solution eliminates the need for dc/dc boost converters and expensive low-profile inductors that are required to meet the height limitations in flip phones. The device requires four small external capacitors for operation: two 1 µF ceramic types for the charge pump, one 10 µF ceramic for Cin and one 10 µF ceramic for Cout. The device operates over a 2.7V to 5.5V input range and can deliver a continuous current of 200 mA. Each charge pump can be independently enabled to extend battery life. A thermal management system protects the device during a short circuit condition by sensing the die temperature and causing thermal shutdown. Integrated soft-start circuitry prevents excessive inrush currents. A low-current shutdown utility reduces quiescent current to less than 1 µA. The device is packaged in a 16-pin QFN (3 mm x 3 mm) for operation over the -40°C to +85°C range. Price is $1.41 each/1,000. ADVANCED ANALOGIC TECHNOLOGIES INC., Sunnyvale, CA. (408) 737-4600.
