Design Of A New GM-APD Array Readout Circuit

The Avalanche Photo Diode(APD)under Geiger Mode(GM)amplifies photoelectric signals with the avalanche multiplication effect of carriers,which has single-photon detection capability.It has been widely used in the fields of 3D imaging,optical communications,medical testing and military surveys.In order to meet the high-precision and high-pixel requirements of single-photon detection technology,APD has developed at the direction of arraying,and the array non-uniformity issue restricts the speed of APD arraying development.Therefore,the readout circuit of GM-APD array is required not only to complete the conversion of photoelectric signals and the quantification of the photon Time of Flight(TOF),but also to correct the array non-uniformity.Studied the generation mechanism of APD array non-uniformity and the quantification principle of photon flight time,this thesis designed a readout circuit that can self-adaptively correct the non-uniformity of APD array,aiming at solving the demand of APD arraying.The readout circuit includes two parts: an interface circuit and a Time to Digital Converter(TDC).The interface circuit serves as a bridge between the detector and TDC,providing a reliable dynamic bias voltage for the detector,and completes the rapid quenching and resetting of the APD detector.At the same time,the output detection signal of the interface circuit is used as the input of TDC for it to complete signal processing.In addition,the interface circuit also adaptively corrects the non-uniformity of each pixel in the APD array to keep the sensitivity of each pixel unit consistent.The TDC adopts an architecture that combines a counter and a Time to Amplitude Conversion(TAC),in which the counter completes coarse counting,and the output result of TAC completes fine counting through the analog-to-digital converter,realizing a large dynamic range and High-resolution photon flight time quantification.This thesis also established an equivalent circuit model of APD for the joint simulation of the detector and the readout circuit.The circuit and layout design of the readout circuit of APD array in this thesis are completed under Global Foundries 0.35?m standard CMOS process conditions.The simulation results show that the quenching delay of the interface circuit is less than 4.22 ns,and the detection delay is less than 3.48 ns,which ensures the reliability of the detector while detecting single-photon signals rapidly.The detection deviation caused by the non-uniformity of the APD array is 2.398 ns before correction,and the one after correction is only 72 ps.It proves that an adaptive correction method is one of the effective technical approaches for the non-uniformity correction of the array.The period of triangle wave signal in TDC is 1?s,and the gain is 100 ps/0.6m V.The quantization range of TDC can be extended to 15 ?s by counter,which meets the requirements of large dynamic range and high resolution.