Autotuning technique for digital constant on-time controllers

This paper addresses the design and practical implementation of a digital constant on-time controller for switched-mode DC-DC converters with self-tuning capabilities. The proposed tuning techniques are based on the sinusoidal signal injection in the control loop in order to measure the linear loop gain transfer function at the desired crossover frequency. This autotuning method is applied in closed-loop condition, hence the stability and the regulation are assured during the tuning process. The proposed tuning technique is presented and the complexity of the control and tuning blocks is analyzed. The proposed approach is simple, accurate, and robust. Experimental results on a 175 A, 1.8 V multiphase buck converter with a constant on-time control IC realized in 0.16μm BCD technology are provided to show the effectiveness of the discussed system.