A switching regulator with quasi-V 2 adaptive on-time (AOT) control, that provides a fast load transient response is proposed. A feed-forward path network allows the proposed switching regulator to achieve a fast transient response and stable operation without requiring an output capacitor with a large equivalent series resistance. The proposed AOT controller makes the switching frequency pseudo fixed in continuous conduction mode and works in pulse-frequency modulation mode under ultra-light load conditions. The AOT controller adjusts the on-time according to the supply voltage load current conditions. The measurement results verify that the switching regulator can operate under load currents of 5-800 mA for supply voltages of 3.3-4.2 V and an output voltage of 1.2 V. The recovery time is 3.6μs and the voltage drop is 55 mV when the load current is increased from 5 to 750 mA.