MAX8805Z

19-0777; Rev 0; 4/07 600mA PWM Step-Down Converters in 2mm x 2mm WLP for WCDMA PA Power General Description The 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 medium- and low-power transmission, and a 60mΩ 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 biasing are also integrated. Two switching frequency options are available—2MHz (MAX8805Y) and 4MHz (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 MAX8805Y/MAX8805Z use an analog input driven by an external DAC to control the output voltage linearly for continuous PA power adjustment. At high duty cycle, the MAX8805Y/MAX8805Z automatically switch to the bypass mode, connecting the input to the output through a low-impedance (60mΩ typ) MOSFET. The www.DataSheet4U.com user can also enable the bypass mode directly through a logic-control input. The LDOs in the MAX8805Y/MAX8805Z are designed for low-noise operation (35µVRMS typ). Each LDO is individually enabled through its own logic control inter...