A Rail-to-Rail high speed continuous time comparator for ToF application

Abstract

The ToF system has a wide range of applications, including automatic driving, 3D reconstruction, and intelligent robot navigation, and more. However, implementing time-of-flight (ToF) systems for measuring real-time distances of objects with varying surface reflectance poses a challenge. The varying reflectivity of object surfaces results in fluctuations in the amplitude of the reflected pulse, causing the input overdrive voltage to the comparator to vary widely. It is a challenge to achieve low propagation delay with small input overdrive. To address this issue, this paper proposes a rail-to-rail high speed continuous time comparator with a new propagation delay optimization circuit. The circuit comprises an automatic clamp circuit and an improved class-AB stage with a clamping function, enabling faster charging and discharging of parasitic capacitances. As a result, the propagation delay for low input overdrive is reduced. The comparator was designed and simulated in 3.3 V, 0.35 µm CMOS process. The simulation results indicate a static power consumption of 10.56 mW. For 5 mV input overdrive, the maximum propagation delay is approximately 9.6 ns.