A8731: Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver

This part is discontinued. Samples are no longer available.

Date of status change: March 4, 2013.

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

The Allegro® A8731 Xenon photoflash charger IC is designed to meet the needs of ultra-low power, small form factor cameras, particularly camera-phones.

The charge time is adjustable by setting the charge current limit from 0.4 to 1.2 A maximum. By using primary-side voltage sensing, the need for a secondary-side resistive voltage divider is eliminated. This has the additional benefit of reducing leakage currents on the secondary side of the transformer. To extend battery life, the A8731 features very low supply current draw—typically 0.01 µA in shutdown mode and 10 µA in standby mode.

The A8731 has a flash dual trigger IGBT driver. The IGBT driver also has internal gate resistors for minimum external component count. The charge and trigger voltage logic thresholds are set at 1.1 V_HI (min) to support applications implementing low voltage control logic.

The A8731 is available in a 10-contact 3 mm × 3 mm DFN package with a 0.75 mm nominal overall package height, and an exposed pad for enhanced thermal performance.

Applications

• Mobile phone flash
• Digital and film camera flash

• Low quiescent current draw (0.01 µA in shutdown mode)
• Primary-side output voltage sensing; no resistor divider required
• User-adjustable current limit from 0.4 to 1.2 A
• 1.1 V logic (V_HI(min)) compatibility
• Integrated IGBT driver with internal gate resistors
• Flexible dual trigger inputs for IGBT driver
• Optimized for mobile phone, 1-cell Li+ battery applications
• No primary-side Schottky diode needed
• Zero-voltage switching for lower loss
• >75% efficiency
• Charge complete indication
• Integrated 40 V DMOS switch