A CMOS 0.18μm 64×64 single photon image sensor with in-pixel 11b time-to-digital converter

Abstract

The design and characterization of a CMOS 64×64 single-photon avalanche-diode (SPAD) array with in-pixel 11b time-to-digital converter (TDC) is presented. It is targeted for time-resolved imaging, in particular 3D imaging. The achieved pixel pitch is 64μm with a fill factor of 3.5%. The chip was fabricated in a 0.18μm standard CMOS technology and implements a double functionality: Time-of-Flight estimation and photon counting. The imager features a programmable time resolution for the array of TDCs from 625ps down to 145ps. The measured accuracy of the minimum time bin is lower than ±1LSB DNL and 1.7LSB INL. The TDC jitter over the full dynamic range is less than 1LSB. Die-to-die process variation and temperature are discarded by auto-calibration. Fast quenching/restore circuit on each pixel lowers the power consumption by limiting the avalanche currents. Time gatedoperation is possible as well.