Photoflash chargers

Linear Technology has released the LT3484 family of ultra-fast photoflash capacitor (typically 320 V) chargers. These ICs are designed as standalone devices, eliminating microprocessor loading and software.

The family is designed for use in digital camera and mobile phone applications where space is at a premium. The device's control technique allows it to use extremely small transformers and the onboard NPN power switch requires no external Schottky diode clamp, reducing size.

Output voltage detection needs no external circuitry as the transformer turns ratio determines final charge voltage.

The devices have an input voltage range of 1.8 to 16, making them suitable for applications powered by two AA alkaline cells or single cell Li-Ion batteries. The LT3484-0, -2 and -1 have primary current limits of 1.4, 1 and 0.7 A, resulting in tightly controlled average input current of 500, 350 and 225 mA. The three versions are otherwise identical.

The Charge pin gives full control of the part to the user. Driving Charge low puts the part in shutdown. The Done pin indicates when the part has completed charging. The LT3484 series is offered in a tiny low profile 2 x 3 mm DFN package.