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 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 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 enable the bypass mode directly through a logic-control input.
The LDOs in the MAX8805W/MAX8805X/MAX8805Y/MAX8805Z are designed for low-noise operation (35µVRMS typ). Each LDO is individually enabled
through its own logic control interface.
The MAX8805W/MAX8805X/MAX8805Y/MAX8805Z are available in a 16-bump, 2mm x 2mm WLP package (0.7mm max height).
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