An 8.5ps Resolution, $2000\mu\mathrm{m}^{2}$ Phase-Domain Delta-Sigma TDC for Lidar Applications

A direct time-of-flight (dToF) lidar is used for distance measurement by detecting the round-trip time of a laser pulse [1]–[4]. Single-photon avalanche diodes (SPADs) have been successfully realized in a CMOS process, and the timing circuit and memory are implemented to store multiple timestamps over conversion cycles. An effective way to detect the timestamps is to detect the arrival time via a time-to-digital converter (TDC), and to sort arrival times into histogram bins. However, as the number of pixels increases, so does the data capacity. This leads to a direct trade-off between distance resolution and the maximum distance range. To address this, partial histogram approaches have been investigated, which successively change the histogram bins by zooming or sliding [3], [4]. However, it requires a significant increase in conversion time or limits distance resolution.