The LP3921 is a fully integrated charger and multi-regulator unit with a fully differential Boomer audio power amplifier designed for CDMA cellular phones. The LP3921 has a highspeed serial interface which allows for the integration and control of a Li-Ion battery charger, 7 low-noise low-dropout (LDO) voltage regulators and a Boomer audio amplifier. The Li-Ion charger integrates a power FET, reverse current blocking diode, sense resistor with current monitor output, and requires only a few external components. Charging is thermally regulated to obtain the most efficient charging rate for a given ambient temperature.