The measurement results showed that the circuit performs as expected and it achieves a CMRR of 82 dB and a maximum SNDR of 36.1 dB with 1-V supply voltage. The total current consumption of the chip, including the output buffer, is only 3 A. Furthermore, the average current consumption of the 8th order bandpass SO-SC filter is very low, since it consumes only about 400 nA, corresponding to 50 nA/pole, which is much less than the current consumption of the SC filters in prior designs. Therefore, the circuit is very suitable for portable ECG measurement applications, like heart rate detectors.
Not sure if anything like this is available commercially though... and of course, using off-the-shelf electronics will cut the costs right down.
SPAD afterpulsing is probably not an issue for this project because it's looking at photon pairs, so uncorrelated random events occurring on all the SPADs won't affect the detection... but will decrease the counting/processing rate by bogging down the electronics.
For measuring concurrent events, I would've thought TTS would be much more critical, and you can't get much better than MCP-PMTs (10-20ps these days?). Just wondering if the same detection could've been done with a multi-anode MCP, although if the sensor is CMOS tech, APDs would probably be easier to incorporate onto an ASIC / SoC.
A company is known by the men it keeps.