The A8732 and A8735 from Allegro MicroSystems Europe are two ultra-small Xenon photoflash charger ICs. They are compact, robust and cost-effective to meet the requirements of very low power, small form-factor cameras and camera phones, says the company. Size and cost are minimised through the level of integration which minimises the number of components used and which are fitted into a 2x2mm DFN package. Battery life is extended by using primary-side voltage sensing to remove the need for a secondary-side voltage divider and associated leakage current. The devices also feature very low supply current in both shutdown and standby mode. The ICs are optimised for use in mobile devices using single-cell lithium batteries, and achieve more than 75% efficiency using zero-voltage switching for lower losses. Capacitor charging is provided by an IGBT driver, while an integrated 50V DMOS switch offers self-clamping protection. The switch current limit in the A8732 can be programmed from 0.45 to 1.5A in 16 steps via a single wire interface, while the current limit for the A8735 is fixed at the popular setting of 1A. The integrated IGBT driver incorporates internal gate resistors for minimum external component count. The charge and trigger voltage logic thresholds are set at 1VHI (minimum) to support mobile-phone applications implementing low-voltage control logic. The devices have a maximum package height of just 0.6mm.
