A CMOS SPAD pixel with an integrated mixed-signal TDC

Abstract:
During the last century, much of the scientific discoveries and advances in the biological field have been derived from the exploration of fluorescence phenomena. This has been possible, in part, thanks to the development of a wide variety of measurement techniques accompanied by high-performance sensing devices. Among these are CMOS Single Photon Avalanche Diodes (SPADs) image sensors, which offer fast response and low fabrication costs. In this work we have developed a pixel with dimensions of 40 µm x 40 µm, which together with a 10 µm SPAD, allows to obtain a 5% fill-factor. In addition, it has an integrated Time-to-Digital Converter (TDC) with a programmable bin width from 100 ps up to 1ns with a total measurement range of up to 72 ns. The pixel architecture will enable fluorescence lifetime measurements of organic and inorganic dyes. The photon arrival time will be used to generate a histogram.