The AAT3688 battery-charger IC for 4.2-V lithium-ion/polymer battery cells operates from a USB port. Its charge-reduction loop monitors the USB port voltage to determine how much power other functions in the portable device are drawing from the USB source. This lets the IC reduce charge time by dynamically adjusting the current while the battery is charging.
Developed by Analogic Tech, the AAT3688 integrates a charging device, a reverse blocking diode, and a current-sensing circuit in a 3- by 3-mm TDFN package. Its input range is 4 to 5.5 V. Charge current can be programmed for USB High and USB Low levels, between 50 and 500 mA, based on port type.
Safety features include the ability to monitor battery temperature and charge state for fault conditions. If a failure is detected, the device shuts down. Status monitor output pins can directly drive two external LEDs to indicate battery status. The AAT3688 costs $1.09 in 1000-piece lots.