Mixed Signal Timing Techniques for SPAD Direct Time-of-Flight Imaging Sensors

The capability of fabricating structures known as SPADs on CMOS processes has led to the development of 3D cameras that measure the time-of-flight of a laser pulse. SPADs sense single-photons with low timing jitter allowing accurate distance measurements, so 2D SPAD arrays that are co-integrated with per-pixel timing circuits can capture a distance image. This thesis investigates mixed signal approaches for photon timing, introducing a digital technique using multistage LFSRs and an analog technique resistant to PVT variation, readout noise, and capacitive discharge. A SPAD sensor combining both techniques is presented demonstrating high linearity, resolution, and a long timing range.