Dual-input charger IC operates from USB or wall adapter
By Paul Rako, Technical Editor -- EDN, January 15, 2009
Advanced Analogic Technologies has introduced the AAT3691 dual-input battery-charger IC with overvoltage protection to 28V with a response time of less than 1 μsec. The IC assesses which input source offers minimum charging time and modifies the charge path accordingly. It can operate from ac-adapter inputs and USB (universal-serial-bus) ports across a 3 to 6.75V range. You can choose resistors to set charge current as high as 1.6A from the wall-adapter input and 0.5A from the USB input. Whenever the wall-adapter or USB input power exceeds 6.75V, an internal series switch opens, preventing damage to the battery or charging circuit. The power path’s on-resistance is 600 mΩ. An input feature lets you suspend charging if no cell is present and protects the circuit from defective battery traces or connectors. Safety features include thermal shutdown protection, power-on reset, and soft start.
The AAT3691 regulates battery-charge voltage and current for 4.2V lithium-ion battery cells in a variety of portable-system applications, such as mobile phones, digital still cameras, and other handheld devices. Because the device incorporates its own overvoltage protection, you need not add this feature externally, reducing space requirements in space-starved handheld-system applications. The AAT3691 comes in a 3×4-mm 16-pin TDFN package, operates in the −40 to +85°C industrial-temperature-range, and sells for $1.12 (1000).
