Inside
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Integrated power supply and audio for wireless systemsProduct Features
Texas Instruments' powerful new TPS9104 integrates a cellphone's
vital power supply and audio power system components into a single
IC. The power supply functions included are three low-dropout
regulators, a microprocessor supply monitor and reset, a 10 mA
charge pump and a 1.185 V bandgap reference. Audio components
contained on the same IC are the speaker and ringer amplifiers
and a low-noise microphone amplifier.
The PMOS design used in the three regulators provides for very low dropout voltages of only 200 mV maximum. The regulator outputs are rated at 100 mA each and are programmable for 3.0 V or 3.3 V. Independent regulator enable inputs may be used to power down circuitry when it is not needed. The use of PMOS series pass transistors in the low dropout regulators reduces operating current to only 120 µA each maximum; standby current is less than 1 µA. The TPS9104 also includes a microprocessor reset that generates a logic low on start up or when the output of the logic regulator falls below the reset trip threshold. This reset output remains in a logic low state for 250 ms after the regulated output reaches its normal range. The charge pump driver allows for implementation of either a voltage doubler or inverter. The device is self-protected against operation in under-voltage and over-temperature conditions. The TPS9104 has two differential-output power amplifiers capable of driving 32-½ dynamic or piezoelectric speakers. Also provided is a high-gain microphone amplifier capable of driving a 10 k½ load. All of the amplifiers have an enable input to reduce supply currents when disabled. On-chip de-popping circuitry prevents unwanted noise when the enable inputs are cycled on or off. This device is offered in a 48-pin thin quad flatpack (TQFP) package.
Vol 19, October, 1996 |
