The TPS9104 incorporates a complete power supply and audio power system for a cellular subscriber terminal that uses battery packs with three or four NiMH/NiCd cells or a single lithium-ion cell. The device includes three low-dropout linear regulators rated for 3.3 V or 3 V at 100 mA each, a charge-pump driver, two power amplifiers for a speaker and a ringer, a low-noise microphone amplifier, and logic that includes a 250-ms reset, on/off control, and processor interface. Regulators A and B and the charge-pump driver are disabled until regulator L (logic regulator) reaches the rated voltage and RESET is logic high. Regulators A and B, the charge-pump driver, and the amplifiers have separate enables allowing circuitry to be powered up or down as necessary to conserve battery power. Each of the amplifiers has a depop circuit to prevent objectionable noise when the IC is powered up or when the amplifiers are enabled. Both the speaker amplifier and the ringer amplifier are designed to supply 2 V peak-to-peak into 32 or into a 90-nF piezoelectric speaker. The microphone amplifier is a low-noise high-gain (AV=100) circuit capable of supplying 3 V peak-to-peak into a 10-k load. The TPS9104 operates over a free-air temperature range of 40C to 85C and is supplied in a 48-pin TQFP package.