MAX8805X

19-0777; Rev 1; 10/07 600mA/650mA PWM Step-Down Converters in 2mm x 2mm WLP for WCDMA PA Power General Description The MAX8805W/MAX8805X/MAX8805Y/MAX8805Z high-frequency step-down converters are optimized for dynamically powering the power amplifier (PA) in WCDMA or NCDMA handsets. The devices integrate a high-efficiency PWM step-down converter for mediumand low-power transmission, and a 60m Ω typical bypass FET to power the PA directly from the battery during high-power transmission. Dual 200mA low-noise, high-PSRR low-dropout regulators (LDOs) for PA biaswww.DataSheet4U.com ing are also integrated. Two switching frequency options are available (2MHz for the MAX8805W/MAX8805Y and 4MHz for the MAX8805X/ MAX8805Z), allowing optimization for smallest solution size or highest efficiency. Fast switching allows the use of small ceramic 2.2µF input and output capacitors while maintaining low ripple voltage. The feedback network is integrated, further reducing external component count and total solution size. The MAX8805W/MAX8805X/MAX8805Y/MAX8805Z use an analog input driven by an external DAC to control the output voltage linearly for continuous PA power adjustment. The REFIN to OUT gain is available in two options (2V/V for the MAX8805Y/MAX8805Z and 2.5V/V for the MAX8805W/MAX8805X). At high-duty cycle, the MAX8805W/MAX8805X/MAX8805Y/MAX8805Z automatically switch to the bypass mode, connecting the input to the output through a low-impedance (60mΩ typ) MOSFET. The user can also en...