A CMOS Time-to-Digital Converter for Real-Time Optical Time-of-Flight Sensing System

The TOF method is the most popular and efficient way to extract depth information in an optical sensing system, and TDC is generally used to measure the round-trip delay. In this article, a TDC with similar to 40 ps measurement resolution and very large linear dynamic range is proposed for optical sensing applications. Referenced to a single 100 MHz clock, the TDC incorporates a DLL and a VDL loop to automatically stabilize the measuring resolution, thus eliminating the need for a separate calibration step before or during actual measurements. The proposed TDC is fabricated using CMOS 0.18 m technology, and its designed characteristics are validated through experiments.