An AOT Buck Converter with Adaptive TON Extender Achieving 2.5µs Settling Time in 4A Load Transient

An adaptive on-time (AOT) buck converter with constant switching frequency and fast transient response is presented. A frequency-locked loop (FLL) is used to achieve constant switching frequency. The on-time (TON) is adjusted by a TON extender to achieve fast transient response. The proposed AOT buck converter is implemented in 0.18µm CMOS process. The simulation results show that the switching frequency is fixed at IMHz under various load condition and the output voltage undershoot and settling time are only 50m V and 2.5µs, respectively during 4A load transient.