A Single Photon Detector Readout Circuit Based on 0.18 μm CMOS Technology.

Single photon detection is currently the key technology in the fields of lidar and three-dimensional imaging. Avalanche photodiode has attracted widespread attention due to their low power consumption, high quantum efficiency, and high speed response characteristics. This paper designs a readout circuit based on a single-photon avalanche diode. The system adopts the active quenching and active recovery front-end circuit, and realizes the avalanche detection threshold voltage adjustment through the 4-bit digital-to-analog converter. In order to reduce the influence of noise, the front-end circuit adopts a gated operating mode, and realizes hold-off time adjustment through a monostable flip-flop, so that the minimum dead time reaches 20 ns. The system has two functions: photon counting and TOF ranging, which are realized by 18-bit asynchronous counter and two-level time-to-digital converter respectively. Corresponding encoding rules are designed for the abnormal conditions of edge sampling. At 500MHz clock frequency, TDC accuracy can reach 250 ps. The system has been designed and implemented in 0.18 μm standard CMOS technology, and the pixel circuit area is 155 μm×155 μm.