This is one of the Controller types.
Part Number : BQ24725A, Marking : BQ25A
Description : 1-4 Cell Li+ Battery SMBus Charge Controller
Package : 20-pin 3.5 × 3.5 mm2 VQFN Type
Manufactures : Texas Instruments
See the preview image and the PDF file for more information.
The bq24725A ( Marking : BQ25A ) is a high-efficiency, synchronous battery charger, offering low component count for space-constraint, multi-chemistry battery charging applications.
The bq24725A utilizes two charge pumps to separately drive n-channel MOSFETs (ACFET, RBFET and BATFET) for automatic system power source selection.
SMBus controlled input current, charge current, and charge voltage DACs allow for very high regulation accuracies that can be easily programmed by the system power management micro-controller.
The bq24725A uses internal input current register or external ILIM pin to throttle down PWM modulation to reduce the charge current.
1. SMBus Host-Controlled NMOS-NMOS Synchronous Buck Converter with Programmable 615kHz, 750kHz, and 885kHz Switching Frequencies
2. Automatic N-channel MOSFET Selection of System Power Source from Adapter or Battery Driven by Internal Charge Pumps
3. Enhanced Safety Features for Over Voltage Protection, Over Current Protection, Battery, Inductor and MOSFET Short Circuit Protection
BQ25A Marking Information
Official Homepage : http://www.ti.com/product/BQ24725A