A Constant On-Time Buck Converter With Analog Time-Optimized On-Time Control

A constant on-time buck converter with analog time-optimized on-time control (OTC) is proposed to achieve fast load-current step-up transient response for high slew-rate loads. The proposed control first implements a constant on-time converter embedded with analog time-optimized OTC and solves the prior art issues such as poor light-load efficiency, high quiescent current, and the dependence on the power stage parameters of OTC. The body diode control, which minimizes the overshoot with simple logic and capacitor-current sensor, is proposed for load current step-down. The proposed control was implemented into an integrated circuit using 0.18 μm CMOS process with a chip area of 1.423 mm
²
, where OTC only occupies 0.054 mm
²
. The simulation results show 51.3% and 55.5% reductions of voltage deviation after enabling the proposed control functions at load step-up and step-down, respectively. Measurement results show that the undershoot of output voltage improves 52.4% after enabling OTC for a 0.84 A load step-up.