General Description

  The LP4054 is a complete constant-current/constant- voltage linear charger for single cell lithium-ion batteries. Its SOT23-5 package and low external component count make the LP4054 ideally  suited  for  portable  applications.  Furthermore,  the LP4054 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 LP4054 automatically terminates the charge cycle when the charge current drops to 1/10th the programmed value after the final float voltage is reached. When the input supply (wall  adapter or  USB  supply)  is  removed,  the  LP4054 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.