The LP4057 is a complete constant-current/constant- voltage linear charger for single cell lithium-ion batteries. Its package and low external component count make the LP4057 ideally suited for portable applications. Furthermore, the LP4057 is specifically designed to work within USB power specifications.No external sense resistor is needed, and no blocking diode is required due to the internal MOSFET architecture. Thermal feedback regulates the charge current to limit the die temperature during high power operation or high ambient temperature. The charge voltage is fixed at 4.2V, and the charge current can be programmed externally with a single resistor.
The LP4057 automatically terminates the charge cycle when the charge current drops to 1.5/10th the programmed value after the final float voltage is reached. When the input supply (wall adapter or USB supply) is removed, the LP4057 automatically enters a low current state, dropping the battery drain current to less than 1μA. Other features include charge current monitor, automatic recharge and a status pin to indicate charge termination and the presence of an input voltage.
