Design Of A High-Performance Timer Circuit For Adaptive On-Time Buck Converter

This paper presents a timer circuit designed for an adaptive on-time (AOT) Buck DC-DC converter. The circuit utilizes input voltage feedforward compensation and output feedback techniques to maintain a constant switching frequency despite fluctuations in input and output voltages, thereby achieving fixed-frequency pseudo pulse width modulation. The design is based on a 0.18 μm BCD process and is validated through Spectre simulations. The simulation results indicate that when the input voltage varies from 4V to 14V, the output voltage change will not exceed 18mV, and the output voltage recovery time is less than 12μs. Furthermore, when the load current jumps between 1A-2A, the output undershoot/overshoot voltage will not exceed 29m V, and the output voltage recovery time is within 27us. Additionally, the incorporation of input voltage feedforward technology enhances the speed of the input linear transient response.