FAN5903 is a high-efficiency, low-noise, synchronous, step-down, DC-DC converter designed for powering 3G/3.5G/4G RF Power Amplifiers (PAs) in handsets and other mobile applications.The output voltage may be dynamically varied from 0.40 V to 3.50 V, proportional to an analog input VCON, ranging from 0.16 V to 1.40 V provided by an external DAC. This allows the PA to be supplied with the voltage that enables maximum power-added efficiency.An integrated bypass FET automatically switches on when battery voltage drops close to the desired output voltage (V-200 mV). The DC-DC switches back to Synchronous Mode when the voltage dropout exceeds 375 mV. The integrated bypass FET is also enabled when V is nominally greater than to 1.5V.The FAN5903 offers fast transition times, enabling changes to the output voltage in less than 10µs for power transitions. Moreover, a Current-Mode control loop with fast transient response ensures excellent line and load regulation.Light-load efficiency is optimized by operating in PFM Mode for load currents typically less than 100mA.The switching frequency may be set to 3 MHz or 6 MHz, enabling further optimization of system performance. The FAN5903 typically uses a single, small-form-factor inductor of 540nH. Efficiency may be further optimized using a 1.0 µH inductor when running at 3 MHz.When output regulation is not required, the FAN5903 may be placed in Sleep Mode by setting V nominally to 50 mV. This ensures a very low I (< 70 µA) while enabling a fast return to output regulation. The FAN5903 enables significant current reduction and increased talk time and is available in a 1.34 mm x 1.29 mm, 9-bump, 0.40 mm-pitch, WLCSP package.
●Features
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● 2.7 V to 5.5 V Input Voltage Range
● VOUT Range from 0.4 V to 3.5 V (or VIN)
● Small Form Factor Inductor
● 2012 540 nH for Minimal PCB Area
● 2520 1.0 µH for Higher Efficiency
● Bypass Dropout at 500 mA, 60 mV Typical
● 100% Duty Cycle for Low Dropout Operation
● Input Under-Voltage Lockout / Thermal Shutdown
● 1.34 mm x 1.29 mm, 9-Bump, 0.4 mm-Pitch WLCSP
● 3 MHz / 6 MHz Selectable Switching Frequency to Facilitate System Optimization
● High-Efficiency PFM Operation at Low Power
● Sleep Mode for Very Low IQ Operation
● Up to 96% Efficient Synchronous Operation at High-Power Conditions
● 10 µs Output Voltage Step Response for Early Power Loop Settling
