A Dark Count Rate Self-Adjusting Charge Pump With Negative Feedback Control for SPAD Array Biasing

This brief introduces an adaptive feedback scheme for voltage bias generation and a novel charge pump feedback circuit for Single Photon Avalanche Diodes (SPADs). The proposed adaptive feedback scheme uses sensing circuit to record the dark count of the SPAD and controls the reference voltage of the charge pump part, achieving the SPAD voltage adjustment according to the Dark Count Rate (DCR). The novel charge pump feedback circuit can realize the stability of the output voltage by controlling the current charging capability of the voltage doublers. The silicon measurement with 180 nm technology shows that the proposed charge pump enables the negative feedback control of DCR and realize the maximum voltage output of 15 V with 3.3 V input voltage. Thanks to the off-chip load capacitance, the output ripple of the charge pump is only 40 mV. Linear growth of DCR is achieved through input configuration signal. After counting DCR of the dummy SPAD for 1 ms, the output voltage changes within one step of 50 mV by judging the DCR level. To the best of the author’s knowledge, the proposed charge pump is the first work to realize a negative feedback voltage control scheme based on the DCR of SPAD. The proposed scheme and circuit provide a promising approach for implementing adaptive voltage bias for SPAD.