Sunnyvale, Calif.—Advanced Analogic Technologies says its AAT3685 is the first chip designed for efficiently charging lithium-ion polymer batteries from either an AC adapter or a USB source through a single connector. The end result is faster battery charging for a given load demand.
"Cell phone and other battery-powered device manufacturers are always trying to give their customers as much flexibility as possible," said Bill Weiss, product line director for battery manager ICs. "Since the AAT3685 can be programmed for two separate constant current charge levels up to 1 amp, users can now charge their device from either an AC source or any USB port without compromising their fast charge rate."
More specifically, says Weis, the chip's 1-amp charge current capability combined with its Charge Reduction Loop provides an edge over competing parts. When working from an AC adapter, the chip charges at the (generally high) rate set by the user. If a USB source is connected, the charge reduction loop limits charge current to the extent necessary to prevent the USB supply voltage from sagging. Thus the loop minimizes the charge time, given a regulated USB port. This dynamic control of charge current allows the fastest possible charge time if the port supply is shared with other systems, and such operation will not overload the charger.
Other products can offer 1-amp capability, and others may shut off when systems share the USB supply, but only the AAT3685 offers the charge reduction loop technique to minimize charge time, says Weiss.
Designed for 4.2-volt battery cells, the AAT3685 combines a charging stage, reverse blocking diode, and current sensing circuit in a compact 3-by-3 mm TDFN package. Battery temperature and charge state are continually monitored for fault conditions. Over-voltage and over-temperature circuits automatically shut down the device in the event of a failure. Status monitor output pins are provided to drive two external LEDs to indicate battery charge status. The device also adds a serial interface output which can report any of 14 different status states to a microcontroller.
Click here for the device datasheet.
The AAT3685 is rated for operation over -40 to +85°C. The device sells for $1.20 each in 1000-unit quantities.
Advanced Analogic Technologies, 1-408-737-4600, www.analogictech.com