A8837: Photoflash Capacitor Charger with IGBT Driver

This device is no longer in production. The device should not be purchased for new design applications. Samples are no longer available.

Date of status change: January 30, 2012.

Recommended substitution: For existing customer transition, and for new customers or new applications, contact Allegro Sales.

The A8837 is a highly integrated IC that charges photoflash capacitors for digital and film cameras. An integrated MOSFET switch drives the transformer in a flyback topology. It also features an integrated IGBT driver that facilitates the flash discharge function and saves board space.

The CHARGE pin enables the A8837 and starts the charging of the output capacitor. When the designated output voltage is reached, the A8837 stops the charging until the CHARGE pin is toggled again. The DONE pin is an open-drain indicator of when the designated output voltage is reached.

The peak current limit can be adjusted to eight different levels between 700 mA and 2 A, by clocking the CHARGE pin. This allows the user to operate the flash even at low battery voltages.

The A8837 can be used with two Alkaline/NiMH/NiCAD or one single-cell Li+ battery connected to the transformer primary. Connect the VIN pin to a 3.0 to 5.5 V supply, which can be either the system rail or the Li+ battery, if used.

Applications include:

• Digital camera flash
• Film camera flash
• Cell phone flash
• Emergency strobe light

The A8837 is available in a very low profile (0.75 mm) 10-contact 3 mm × 3 mm MLP/TDFN package, making it ideal for space-constrained applications. It is lead (Pb) free, with 100% matte-tin leadframe plating.

• Power with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries
• Eight-level, digitally-programmable current limits from 700 mA to 2 A
• Voltage sensing feedback before output diode for low leakage
• Adjustable output voltage
• No primary-side Schottky diode needed
• Integrated IGBT driver with trigger
• Charge complete indication
• >75% efficiency
• Low-profile (0.75 mm high) 3 mm × 3 mm MLP/TDFN
• 10-contact package