The TPS9103 is a fully-integrated power supply for depletion-mode GaAs power amplifiers in wireless communications equipments. It is the first GaAs PA power supply with an integrated high-side p-channel MOSFET switch for delivering power to the RF power amp. The MOSFET has a maximum on-resistance, RDS(on), of 180 m, and logic-compatible input. The TPS9103 also contains a charge pump to develop negative gate-bias voltage, and logic to prevent turn-on of the high-side switch until the gate bias is present.
Discrete RF power amplifier designs require careful attention to the switching of battery power to the GaAs FET switch, ensuring that proper gate bias is applied first to avoid destroying the FET. Logic to control power switching and to conserve power when not in use must be added. The TPS9103 greatly simplifies RF power supply design by integrating all these functions in a single chip.
The TPS9103 features a standby mode, reducing power consumption to 10 µA (max). Supply current during operation is a maximum 500 µA. The TPS9103 has its own 50-kHz charge pump oscillator, or can be synchronized to an external clock. The clock signal is buffered and available to drive an external charge pump. The TPS9103 also includes undervoltage lockout (UVLO) protection to prevent operation when battery voltage is too low.
Applications for the TPS9103 include cellular handsets, base stations,
PDAs, portable facsimile (fax) machines, and other wireless communications
equipment. The TPS9103 is available in a very low profile 20-pin
TSSOP package.
Vol 18, August, 1996
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