onsemi FAN5903BUCX

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_OUT = V_BAT - 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_CON is nominally greater than to 1.5 V. The FAN5903 offers fast transition times, enabling changes to the output voltage in less than 10 μs 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 100 mA.

• 2.7 V to 5.5 V Input Voltage Range
• V_out Range from 0.4 V to 3.5 V (or V_IN)
• Small Form Factor Inductor: 2012 470 nH or 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×1.29 mm, 9-Bump, 0.4 mm-Pitch, Wafer-Level Chip-Scale Package (WLCSP)
• 3 MHz / 6 MHz Selectable Switching Frequency to Facilitate System Optimization
• High-Efficiency PFM Operation at Low Power
• Sleep Mode for Very Low I_Q Operation
• Up to 96% Efficient Synchronous Operation at High-Power Conditions
• 10 μs Output Voltage Step Response for Early Power Loop Settling

• Dynamic Supply Bias for 3G/3.5G and 4G PAs
• Power Supply for WCDMA/LTE PAs