Description
The SC250 is a synchronous step-down converter designed specifically for use as an adaptive voltage supply for CDMA and WCDMA RF Power Amplifiers (PAs). The output voltage can be adjusted dynamically between 0.3V and (Vin - 0.4)V through a linear analog control input. For high power operation, a maximum control input signal level forces the device into bypass mode where the input is connected directly to the output via an internal PChannel pass transistor. Bypass mode also occurs when the output load demands duty cycles in excess of the maximum rated duty cycle.

Features
◆ Adjustable output voltage range — 0.3 to 3.6V
◆ Linearly proportional VDAC to VOUT relationship for increased PA efficiency
◆ Pass-through mode automatic and on demand
◆ Input voltage range — 2.7V to 5V
◆ Typical settling time — 40μs
◆ Output current capability — 600mA
◆ Maximum output current in bypass mode — 1A
◆ Up to 96% efficiency
◆ Constant frequency operation — 1MHz
◆ Less than 1μA shutdown current
◆ Internal 75mΩ PMOS bypass transistor
◆ PA bias voltage supply — 2.85V, 20mA, 1.5%
◆ MLPD-W8, 2.3 x 2.3mm package

Applications
◆ CDMA and WCDMA Phones
◆ Handheld Radios
◆ RF PC Cards
◆ Battery Powered RF Devices