The output capacitor selection is also a critical part of the design. The output capacitance determines the load transient performance of the power supply. The output capacitance is required to minimize the voltage overshoot and ripple present at the output of a step-down converter. Poor load transient performance or instability is often caused by insufficient output capacitance, and large voltage ripple is caused by insufficient capacitance as well as a high equivalent series resistance (ESR) in the output capacitor. The maximum allowed output voltage overshoot and ripple are usually specified at the time of design. Thus, to meet the ripple specification for a step-down converter circuit, designers must include an output capacitor with enough capacitance and low ESR.