Active-Reset for the N+P Single-Ended SPAD Used in the NIR LiDAR Receivers

A monolithic resistorless circuit has been designed for active reset of the N
⁺
P single-ended (common anode) single-photon avalanche diode (SPAD). This type of SPAD has enhanced the photon detection efficiency in the near-infrared (NIR) region relatively to the P
⁺
N (two-ended) SPAD. Due to this fact, the N
⁺
P SPAD is a better candidate for the light detection and range (LiDAR) working in the NIR region. The circuit is fabricated in a standard 0.18-μm CMOS image sensor process. The dead time after each photon detection is adjustable; the minimum measured value is 4 ns. The maximum photon count rate corresponding to this dead time is 2.5·10
⁸
photons/s. This circuit guarantees precise repeatable response, short and well-controlled dead time, and after-pulsing effect reduction. All these are essential for many SPAD applications and crucial for increasing the saturation level of the silicon photo multiplier (SiPM)based LiDAR systems working in strong background light conditions on sunny day.