The SC251 is a synchronous step-down converter designed for use as an adaptive voltage supply for WCDMA RF power amplifiers (PAs). An analog control input is used to adjust the output voltage dynamically between 0.5V and 3.4V using a non-linear transfer function. The non-linear relationship maximizes total system efficiency by providing the PA with the minimum voltage it needs to maintain linearity. For output voltages greater than 3.4V the input is connected directly to the output via an internal PMOS switch. An optional gate drive (GD) output to control an external low on-resistance PMOS switch is also provided for systems applications that require minimal voltage drop. The SC251 also provides a 2.85V LDO reference output that can be used to supply a PA bias input.