D. E. Schwartz, E. Charbon, and K. L. Shepard, “A single-photon avalanche diode imager for fluorescence lifetime applications” Symposium on VLSI Circuits, 2007, pp. 144-245.

A 64-by-64-pixel CMOS single-photon avalanche diode (SPAD) imager for time-resolved fluorescence detection features actively quenched and reset pixels, allowing gated detection to eliminate pile-up nonlinearities common to most time-correlated single-photon counting (TCSPC) approaches. Reset Timing information is collected using an on-chip time-tocalb calibrated digital converter (TDC) based on a counter and a supply- interpolators regulated delay-locked loop (DLL).