Small area 0.3 pJ/conv, 45 ps time-to-digital converter for arrays of silicon photomultiplier interfaces in 150 nm CMOS

A ring-oscillator-based time-to-digital converter (TDC) is presented which can achieve a figure-of-merit of 0.3 pJ/conv in a very small footprint of 0.0024 mm². Thanks to the optimisation of the ring-oscillator and of the sub-cycle interpolation, a 45-ps LSB is obtained with only 0.95 mW of power consumption. The area and power characteristics make the TDC suitable for its use in repeated instances, such as in multiple silicon photomultipliers readout channels or single-photon imaging devices with time-correlated detection.