Implementing a Simple Sigma-Delta ADC in Low-cost FPGA for SiPM-based Nuclear Imaging Systems

This paper describes a simple, low-cost, and scalable readout electronics based on sigma-delta modulation for silicon photomultipliers (SiPM) used in nuclear imaging systems. For energy measurements, the proposed readout design needs only one resistor, one capacitor, and a field-programmable gate array (FPGA) without using any external analog-to-digital convertor (ADC). In this paper, we introduce the new readout electronics and present our preliminary energy measurement results with CsI(Tl), LYSO, and GAGG crystals optically coupled to Onsemi’s J-Series SiPMs. Our preliminary measurement results show that the proposed readout electronics design is able to achieve energy resolutions (FWHM) of 7.2 %, 12.0 %, and 10.9% from 511 keV gamma-rays in $\operatorname{CsI}(\mathrm{Tl})$, LYSO, and GAGG detectors, respectively.