Voltage-scaling step-down converter works with CDMA, WCDMA PAs - Embedded.com

Voltage-scaling step-down converter works with CDMA, WCDMA PAs


The AAT1171 is a fully-integrated voltage-scaling dc-to-dc step-down converter that's optimized to control the power to the power amplifier (PA) in WCDMA and CDMA handsets. By dynamically controlling the PA's operating voltage, the part increases amplifier efficiency and extends talk time.

Developed by Advanced Analogic Technologies (AnalogicTech), the AAT1171 operates across a voltage input range of 2.7 to 5.5 V. Its input voltage is controlled by a real-time output signal from the baseband processor and delivers up to 600 mA of continuous load current.

By supplying a variable output voltage of 0.6 to 3.6 V, the AAT1171 optimizes PA efficiency at both low and high transmit levels. To meet stringent WCDMA requirements, the output voltage responds in less than 30 μs. No load quiescent current is 45 μA (typical).

The AAT1171 maximizes efficiency and extends handset talk time by providing an integrated 85-mω bypass MOSFET. When transmitting at full power, the MOSFET switch bypasses the dc-to-dc converter and output inductor to provide a low resistance path between the battery and the PA. The switch is activated by setting the bypass input high or forcing the baseband DAC voltage output to 1.3 V.

The AAT1171 is immediately available in a Pb-free, 12-pin TDFN33 package. The device sells for $1.31 each in 1000-piece quantities. For more information, visit www.analogictech.com.

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