Description

The LTC4057 is a constant-current/constant-voltage linearcharger for single-cell lithium-ion batteries. ItsThinSOT™ package and low external component countmake the LTC4057 especially well suited for portableapplications. Furthermore, the LTC4057 is specificallydesigned to work within USB power specifications.No external sense resistor is needed and no blocking diodeis required due to the internal MOSFET architecture.Thermal feedback prevents overheating by regulating thecharge current to limit the die temperature during highpower operation or high ambient temperature conditions.The charge voltage is preset at 4.2V and the charge currentcan be programmed externally with a single resistor.When the input supply (wall adapter or USB supply) isremoved, the LTC4057 automatically enters a low currentstate, dropping the battery drain current to less than 2µA.With power applied, the LTC4057 can be put into shutdownmode, reducing the supply current to 25µA.For the standalone version (on-board charge termination)of the LTC4057, refer to the LTC4054.Applications Wireless PDAs Cellular Phones Portable Electronics