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A switching regulator with quasi-V2 adaptive on-time (AOT) control that provides a fast load transient response is proposed in this paper. The feed-forward path network allows the proposed switching regulator to achieve a fast transient response and stable operation without requiring an output capacitor with large equivalent series resistance. The proposed adaptive on-time controller makes the switching frequency pseudofixed in the continuous conduction mode and works in the pulse-frequency modulation mode under ultralight-load conditions to maintain the conversion efficiency. The AOT controller adjusts the on-time according to the supply voltage and load current conditions. The measurement results verify that the switching regulator can operate under load current between 5 and 800 mA for the supply voltage of 3.3-4.2 V and an output voltage of 1.2 V. The recovery time is 3.6 μs and the voltage drop is 75 mV when the load current is increased from 5 to 750 mA.