SPAD array for LiDAR with region-of-interest selection and smart TDC routing

Light Detection and Ranging (LiDAR) is a technique that can be applied to identify the position of objects in an industrial environment, which usually suffer by strong background illumination. In this work we present a novel architecture of a Single Photon Avalanche Diode (SPAD) array optimized for a direct Time Of Flight (dTOF) single-point rangefinder system, with a distance range of about 2 m and a resolution of a few centimeters. The ASIC has been implemented in a 0.16 μm Bipolar-CMOS-DMOS (BCD) technology and includes 10 × 40 pixels, 80 Time-to-Digital Converters (TDCs), and a histogram builder. The peculiarity of this work is the ability of performing a Region-Of-Interest (ROI) selection of just those pixels illuminated by the laser spot, as well as a smart sharing of timing electronics. ROI selection is performed through SPADconnected up/down counters, that are decremented whenever the connected SPAD is triggered within the time window where the laser spot is expected, whereas they are incremented when the connected SPAD is triggered within a time window where the laser pulse is not present. If the counter stores a negative value, the pixel is considered to be within the laser spot, and just those pixels might trigger a TDC during the following 500 samples frame. Each TDC is shared among 5 non-adjacent pixels that should not be hit at the same time, considering the expected laser spot dimension. The implemented TDCs have 75 ps resolution and 19.2 ns Full Scale Range (FSR).