The XC9303 series is highly efficient, synchronous PWM, PWM/PFM switching step-up & down DC/DC controller ICs. A versatile, large output current and high efficiency, step-up/down DC/DC controller can be realized using only basic external components - transistors, coil, diode, capacitors, and resistors for detecting voltages. High efficiency is obtained through the use of a synchronous rectification topology. The operation of the XC9303 series can be switched between synchronous PWM and synchronous PWM/PFM (autoswitching) externally using PWM pin. In PWM/PFM mode the XC9303 automatically switches from PWM to PFM during light loads and high efficiencies can be achieved over a wide range of output loads conditions. Output noise can be easily reduced with PWM control since the frequency is fixed.