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 c. 10⁸ 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.