A SPAD Readout Circuit Based on Column-Level Event-Driven Time-to-Digital Converter

3D sensing technology with SPAD as the core device is used in many fields. Such 3D sensing systems based on frame mode mainly consist of front-end circuit and per-pixel level TDCs, which usually have large power consumption and generate a large amount of redundant data in some application scenarios. In this paper, we innovatively propose an event-based column level multi-event time to digital converter. The column-level TDC Chain consists of multiple TDC units that can record the time-of-flight information of the event in the pixel array output bus in turn under the enable control, with no global clock signal in the system. Readout circuity is event-driven, with data output is realized through an asynchronous arbitration module. The designed circuit is validated using a 180nm standard CMOS process, and the time required for the TDC to record a single event is about 5.3ns. The TDC Chain composed of four cells can measure a maximum input event stream with a frequency of 650MHz. System power consumption can be reduced as event stream rate decreases, enabling event-driven dynamic power adjustment.