Dual buck converter extends battery life in 3G handsets

Maxim Integrated Products introduces the MAX8896, a dual step-down converter designed for powering WCDMA/NCDMA PA (power amplifier) modules and RF transceivers. This 4-mm2 device integrates a high-efficiency, PA step-down converter 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 MAX8896 also includes an RF step-down converter that supplies a high-PSRR, low-noise LDO (low-dropout linear voltage regulator) to provide a high-efficiency voltage supply for the RF transceiver. The MAX8896 is well suited for multiband WCDMA/NCDMA applications such as cellular handsets, netbooks, and smartphones. The MAX8896 is available in the Infineon SMARTi UE HSPA RF transceiver and the XMM 6160 mobile phone platform, providing users with excellent battery life.

Supporting 1.9 A of peak current, the integrated low-impedance 140 milliohm 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 2 MHz fixed switching frequency. It supports a 100% duty cycle, and provides a fixed 3.1 V output voltage with ±2% output-voltage accuracy. The high-PSRR (65 dB), low-noise (16 microVrms), 2.8V LDO delivers a guaranteed 200 mA output current. The low-noise output makes this LDO suitable for RF transceiver biasing or applications that require an exceptionally clean power source. The MAX8896 is offered in a tiny, 2 x 2 mm, 16-bump UCSP package (0.7 mm height, max) and is fully specified over the -40° to 85° C extended temperature range.

For more information, contact Maxim Integrated Products, 120 San Gabriel Dr., Sunnyvale, CA 94086. Phone: (408) 737-7600.