Objective Single photon avalanche diode (SPAD) is extensively applied in low-light detection scenarios, such as LIDAR, quantum communication and fluorescence spectroscopy, owing to its attributes of rapid response, strong anti-interference capabilities, compact form factor and low power consumption. In these applications, operation in Geiger Mode (GM) involves applying a reverse bias voltage surpassing the intrinsic avalanche breakdown voltage, endowing the SPAD with single-photon detection sensitivity. The ensuing avalanche current triggered by a single-photon signal necessitates immediate quenching to prevent sensor overcurrent damage. Achieving this quenching, coupled with prompt detector reset a standby state, is facilitated by the quenching circuit. The rapid quenching time of this circuit assumes critical importance in ensuring SPAD reliability and sustaining a high photon detection rate. The resistor R\mathrm_S can quickly sense avalanche current and also play a role in quenching. However, the resistance R\mathrm_S will lead to an RC delay in the passive quenching stage, which will slow down the quenching speed. Therefore, it is necessary to obtain the optimal value range of induction resistance. For this purpose, through mathematical model analyzing, a quenching circuit is designed in this paper.
Methods A fast active-passive mixed quenching circuit structure is designed in this paper (Fig.9). The value of the inductive resistance R\mathrm_S is optimized to improve the relevant performance of the quenching circuit. The improvement of delay performance when the resistance increases can be combined with the overhead of layout area to draw the corresponding “cost performance” curve. When the block resistance value is constant, the increase of resistance value is linear with the consumption of area. Even if there are some differences in the intrinsic parameters of the detector due to the non-uniformity of the array, the values of the inductive resistance in the interface circuit have approximately the same best “cost performance” value.
Results and Discussions Through mathematical model analyzing, the inductive resistance value R\mathrm_S is set to20 kΩ. The layout of the proposed quenching circuit is designed in TSMC 0.35 μm CMOS technology. The main function and performance of the circuit are tested. The delay caused by parasitic capacitance carried by the probe is taken into account. The chip test results show that the quenching time of the circuit is about 2.9 ns and the resetting time is about 1.75 ns (Fig.11). Considering that the circuit designed in this paper not only integrates the avalanche quenching circuit, but also integrates the circuit of wide range dead-time adjustment, therefore, the circuit designed in this paper using the optimized fast quenching structure has a high "cost performance"(Tab.1).
Conclusions Based on the detection and imaging application of SPAD in Geiger mode, a rapid quenching circuit is designed in this paper. The circuit adopts a fast active-passive mixed quenching structure, and the quenching time performance of the circuit is optimized. Combined with the layout area, the best value of induction resistance when the detector parameters change in a certain range is obtained. In addition, the circuit layout design and tape-out are completed based on TSMC 0.35 μm CMOS process. The chip test results show that the quenching time of the circuit is about 2.9 ns and the resetting time is about 1.75 ns.
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