Direct Time-of-Flight Sensor System Based on SPAD IC

In recent years, direct time-of-flight (dToF) sensor systems have become crucial in autonomous vehicles, light detection and ranging (LiDAR), and 3D imaging applications. Single-photon avalanche diodes (SPADs), highly-sensitive detectors capable of capturing individual photons, play a vital role in the systems by enabling high-resolution imaging and accurate distance measurement. Time-to-digital converters (TDCs) are crucial for dToF systems as they allow for high-precision, picosecond-level measurements by converting time intervals into digital values. In this paper, we present the design of TDC using a voltage-controlled Vernier delay line. We also show simulation results of the dToF system, which include the analog front-end (AFE) for the SPAD, TDC, and FPGA-based histogram, using a Verilog-A SPAD model based on SPAD's characteristics.