Active quenching for single-photon avalanche diode using one- shot circuit

A method for operating a Single Photon Avalanche Diode-based (SPAD-based) sensor circuit, the SPAD-based sensor circuit including at least one Single Photon Avalanche Diode (SPAD) having an anode and a cathode, the anode being connected to a fixed voltage source, the SPAD being configured to maintain a potential on the cathode at a first voltage level that is greater than a breakdown voltage of the SPAD in the absence of a triggering event, and configured to undergo avalanche breakdown when subjected to said triggering event until the potential on the cathode drops from the first voltage level to a second voltage level that is less than the breakdown voltage, wherein the method comprises:

• before each said triggering event, coupling the SPAD to a bias voltage source by actuating a quenching transistor such that the potential on the cathode is maintained at the first voltage level;
• during each said triggering event:
• de-coupling the SPAD from the bias voltage source by de-actuating the quenching transistor until the potential on the cathode of the SPAD stabilizes at the second voltage level;
• and then
• re-coupling the SPAD to the bias voltage source after a fixed delay period by re-actuating the quenching transistor such that the potential on the cathode of the SPAD is reset to the first voltage level.

A light detection and ranging (LIDAR) system comprising:

• a light source configured to emit pulses of near-infra-red (NIR) light as an output beam;
• means for scanning the output beam toward a light source field of view and for receiving reflected or scattered portions of the output beam as an input beam;
• and
• a sensor circuit configured to receive the input beam, wherein the sensor circuit comprises:
• at least one enhanced-NIR Single Photon Avalanche Diode (SPAD) having an anode and a cathode, said anode being connected to a fixed voltage source, the SPAD being configured to maintain a potential on the cathode at a first voltage level that is greater than a breakdown voltage of the SPAD in the absence of a triggering event, and configured to undergo avalanche breakdown when subjected to said triggering event until the potential drops from the first voltage to a second voltage below the breakdown voltage;
• and
• an active quenching circuit including:
• a quenching transistor having a first terminal connected to a bias voltage source and a second terminal connected to the cathode of the SPAD;
• a one-shot circuit having an input terminal coupled to the cathode of the SPAD, and an output terminal coupled to a control terminal of the quenching transistor,
• wherein the one-shot circuit is operably configured such that, in response to each said triggering event, said one-shot circuit generates a first output signal that de-actuates said quenching transistor to isolate the SPAD from the bias voltage source, and then after a predetermined delay period during which the potential on the cathode stabilizes at the second voltage, the one-shot circuit generates a second output signal that re-actuates said quenching transistor, whereby the SPAD is coupled to the bias voltage source such that potential on the cathode is restored to the first voltage level.