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The FAN5902 is a high-efficiency, low-noise, synchronous, step-down DC-to-DC converter designed for powering the radio frequency power amplifiers (RFPA) in 3G mobile handsets and other mobile applications. It provides up to 800mA of output current over an input voltage range of 2.7V to 5.5V. The output voltage can be dynamically adjusted from 0.4V up to 3.4V, proportional to an analog input voltage ranging from 0.2V to 1.7V provided by an external DAC. This allows supplying the RFPA with the voltage level that provides optimum Power Added Efficiency (PAE).
An integrated bypass FET automatically switches on when the battery voltage drops too close to the output voltage (when VOUT=VBAT-250mV). The bypass transition is controlled by a slew rate controller to limit the inrush current and reduce the RFPA gain deviation.
The FAN5902 offers fast transition times, allowing changes to the output voltage in less than 20µs.
The FAN5902 operates at 6MHz, enabling the use of a small, low-value inductor of 470nH. A current-mode control loop with fast transient response ensures excellent line and load regulation.
The FAN5902 improves the RFPA power efficiency and increases the talk/connection time in 3G handsets.
The FAN5902 is available in a 12-lead MLP package and 12-bump WLCSP.
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