A High Accuracy Constant-On-Time Buck Converter with Spur-Free On-Time Generator

A buck converter with good load regulation and spur-free on-time generator (SFOTG) is presented in this work. The proposed control scheme adopts an additional current feed-forward circuit and a type-II compensator to eliminate dependency on the equivalent series resistance (R
_ESR
) of the output capacitor (C
_OUT
) to ensure an accurate output voltage (V
_OUT
). Furthermore, SFOTG is employed to reduce electromagnetic interference (EMI) effects for noise-sensitive applications. This work is implemented in the TSMC 0.18-μm CMOS process. The chip active area is 0.7 mm
²
. Experimental results demonstrate the load regulation of 1.8 mV/A, and 20.73-dB improvement of the output spurs compared to that of a conventional COT buck converter. The peak efficiency is 89.1% at 300 mA load current.