A CMOS sensor based on single photon avalanche diode for fluorescence lifetime measurements

This paper describes the design of a 7x2-pixels array, fabricated in a high voltage 0.35-mu m CMOS technology, and specifically conceived for fluorescence lifetime measurements. The incident light is detected using a photodiode biased above its breakdown voltage so that an extremely high sensitivity can be achieved exploiting the intrinsic multiplication effect of the avalanche phenomenon. A single photon avalanche diode combined with an active quenching circuit and a 17-bit digital events counter have been implemented in a 180x150-mu m(2) pixel. On chip master logic provides the digital control phases required by the pixel array with a fully programmability of the main timing synchronisms. A maximum operating frequency of 40MHz and an observation window within the 0-128ns range with a 0.5ns step are expected.