The XC9220/XC9221 series is a group of multi-purpose step-down DC/DC controller ICs. The ICs enable a high efficiency, stable power supply with an output current up to 3A to be configured using only a transistor, a coil, a diode, and two capacitors connected externally. Low ESR capacitors such as a ceramic capacitor can be used as an output capacitor. The XC9220/XC9221 series has a 0.9V (1.5%) reference voltage, and using externally connected resistors, the output voltage can be set freely. With an internal switching frequency of 300kHz and 500kHz 1.0MHz, small external components can also be used. The XC9220 series is PWM control, and the XC9221 series is PWM/PFM mode, which automatically switches from PWM to PFM during light loads and high efficiencies can be achieved over a wide range of load conditions. As for the soft-start time, the XC9220/XC9221A and C series is internally set to 4msec and the XC9220/XC9221B and D series can be externally set-up. With the built-in U.V.L.O. (Under Voltage Lock Out) function, the internal P-channel driver transistor is forced OFF when input voltage becomes 2.3V or lower.