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 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).