The LP3923 is a fully Integrated Power Management Unit (PMU) designed for CDMA cellular phones. The LP3923 PMU contains a fully integrated Li-Ion battery charger with power FET and over-voltage-protection (OVP), one Buck regulator, 8 low-noise low-dropout (LDO) voltage regulators, and a high-speed serial interface to program on/off conditions and output voltages of individual regulators, and to read status information of the PMU. Two LILO (low-input, low-output) type LDOs with separate power input provide an application option for pre-regulated high efficient power management for longer battery life. The Li-Ion charger can safely charge and maintain a single cell Li-Ion battery operating from an AC adapter. The charger integrates a power FET, a reverse current blocking diode, a 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. A built-in Over-Voltage Protection (OVP) circuit at the charger inputs protects the PMU from input voltages up to +28V, eliminating the need for any external protection circuitry. Buck regulator has an automatic switch to PFM mode at low load conditions providing very good efficiency at low output currents. An external divider circuitry provides user defined buck output voltage. A-type LDO regulators provide excellent PSRR and very low noise, 10 µV typ., ideally suited for supplying voltage to RF and other analog sections.