A charge-transfer analog counting readout circuit based on pulse rising edge trigger

Abstract

The invention discloses a charge transfer type analog count reading circuit based on pulse rising edge triggering. The circuit comprises 13 MOSFET transistors, an integral capacitor and a parasitic capacitor. The MP1 and MP2 are a charge injection switch and a charge transfer switch and are used for controlling generation and transfer of a charge packet. The parasitic capacitor Cgd bridged between a gate and a drain of the MP1 couples an input avalanche pulse signal into the drain of the MP1. The MP4 and MN1 form a reset circuit which is used for discharging charges stored by the integral capacitor. The MP6, MP7, MP8, MN2, MN3 and MN4 form a unit gain amplifier which is used for preventing a voltage of the integral capacitor from being influenced by electric leakage of the MOSFET transistor connected with the integral capacitor C. The MP3 is a source follower transistor. The MP5 is a load. The MP9 is a lien selection transistor. The voltage on the integral capacitor C is read to an external circuit through the MP3 and the MP9. According to the analog count reading circuit, a wide count range can be realized, moreover, an area of SPAD array detector pixel units can be reduced, and the density of an SPAD array detector is improved.

Description

technical field [0001] The invention relates to a charge-transfer type analog counting readout circuit triggered by pulse rising edge, which belongs to the field of optoelectronic technology. Background technique [0002] Single-photon avalanche diode (SPAD) has been widely used in bioluminescent lifetime imaging, Raman spectroscopy, 3D imaging and other technical fields due to its high sensitivity and sub-second time resolution. At present, single-photon avalanche diodes are developing towards low-cost, high-density, high-reliability deep submicron CMOS process array image sensors. A SPAD array detector includes numerous SPAD pixel units and peripheral readout and control circuits. In order to increase the density of the SPAD array detector, the area of ​​the SPAD pixel unit must be reduced. Each SPAD pixel unit is composed of a SPAD device, a quenching reset circuit and a counting readout circuit. Traditional counting circuits all use digital counting circuits, which hav...

AI Technical Summary

Problems solved by technology

The simple analog counting circuit proposed earlier is sensitive to the pulse width of the input avalanche pulse, requires a large integral capacitor, and the uniformity of the counting step is poor

Later, an analog counting circuit based on charge sharing was proposed. Although the uniformity between different pixel units was improved, the linearity of the counting step was poor.

In order to solve the problem of poor linearity, a level-triggered charge-transfer analog counting circuit is proposed, but an integration capacitor of 350fF is still required to achieve an 8-bit counting resolution. If a higher bit resolution is achieved, the counting circuit area is still large

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