The project presents the on – chip digitization of an analog silicon photomultiplier’s (SiPM) fast output to pave the way to higher granularity in the digital conversion of photon detection. The fast output represents a unique feature developed by SensL by adding a third terminal (in addition of anode and cathode) capable of carrying ultra-fast output signals. The signal is used to make ultra-fast timing measurements having a very small capacitance which makes it suitable for readout systems [1]. Combining the photodetector together with on-chip electronics brings advantages such as internal parasitic reduction, simplicity and compactness. Moreover, the integration allows to perform capacitive decoupling, comparison and conversion on-chip. The main components of the entire system are the C-Series analog SiPM developed by SensL, a time-to-digital converter and comparator which serve as readout circuits [2]. The design was implemented in 0.35µm CMOS technology. The analog SiPM presents a photon detection efficiency of 48% at 420nm wavelength. The entire electronics occupies small area on the chip, representing negligible loss of fill factor. The overall sensor’s fill factor is 75% for a sensitive area of 3×3mm2. TDC simulation results indicate a DNL of ±0.55LSB and an INL of ±1LSB and a typical resolution of 65ps LSB. A conceptual diagram of the system is presented in the figure below.
References:
[1] http://sensl.com/downloads/ds/DS-MicroJseries.pdf
[2] A. Muntean, E. Venialgo, S. Gnecchi, C. Jackson and E. Charbon, ‘’Towards a fully digital state-of-the-art analog SiPM,’’ IEEE Nuclear Science Symposium and Medical Imaging Conference, 2017.
Collaboration
