Power
MAX8896: Dual buck converter powers the WCDMA PA and RF transceiver to extend battery life in 3G handsets
Maxim introduced the MAX8896, a dual step-down converter designed for powering WCDMA/NCDMA PA (power amplifier) modules and RF transceivers. This 4mm2 device integrates a high-efficiency, PA step-down converter that is optimized for medium- and low-power transmission, and includes a bypass FET for powering the PA directly from the battery during high-power transmission. By using the MAX8896 between the battery and RF-transceiver/PA, designers can reduce current consumption by up to 50% under typical operating conditions, thus extending battery life.
The Supporting 1.9A of peak current, the integrated low-impedance 140milliohm (typ) bypass FET provides maximum power with minimum dropout, even under low-battery conditions. During high-power transmission, the bypass FET automatically turns on if the required output voltage is within 99% of the input voltage, and the PA step-down converter is forced into a 100% duty cycle.
The RF step-down converter has 94% peak efficiency with a 2MHz fixed switching frequency. It supports a 100% duty cycle, and provides a fixed 3.1V output voltage with ±2% output-voltage accuracy. The high-PSRR (65dB), low-noise (16microVrms), 2.8V LDO delivers a guaranteed 200mA output current. The low-noise output makes this LDO ideal for RF transceiver biasing or applications that require an exceptionally clean power source.