基于A8735的超低功耗閃光燈充電方案

Allegro 公司的A8735是超低功耗Xenon閃光燈充電集成電路,封裝尺寸只有2x2mm,關斷模式的電流僅為0.5uA,峰值電流1A限制,效率大于75%,很適合用于手機單個鋰離子電池充電以及小型照相機.本文介紹了A8735主要特性和優勢, 功能方框圖,典型應用電路圖以及推薦的PCB布局圖.

The Allegro? A8735 is a Xenon photoflash charger IC designed to meet the needs of ultra low power, small form factor cameras, particularly camera phones. 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 A8735 features very low supply current draw (0.5 μA max in shutdown mode). The IGBT driver also has internal gate resistors for minimum external component count. The charge and trigger voltage logic thresholds are set at 1 VHI(min) to support applications implementing low-voltage control logic.

The A8735 is available in an 8-contact 2 mm × 2 mm DFN/MLP package with a 0.60 maximum overall package height, and an exposed pad for enhanced thermal performance. It is lead (Pb) free with 100% matte tin leadframe plating.

A8735主要特性和優勢:

? Ultra small 2 × 2 DFN/MLP-8 package

? Low quiescent current draw (0.5 μA max. in shutdown mode)

? Primary-side output voltage sensing; no resistor divider required

? Fixed 1 A peak current limit

? 1V logic (VHI(min)) compatibility

? Integrated IGBT driver with internal gate resistors

? Optimized for mobile phone, 1-cell Li+ battery applications

? Zero-voltage switching for lower loss

? >75% efficiency

? Charge complete indication

? Integrated 50 V DMOS switch with self-clamping protection

圖1.A8735功能方框圖

圖2.A8735單電源應用電路圖

圖3.A8735帶單獨偏壓電源的應用電路圖

圖4.A8735推薦的應用電路圖

圖5.A8735推薦的元件布局圖