Multipurpose, Fully-Integrated 128×128 Event-Driven MD-SiPM with 512 16-Bit TDCs with 45 PS LSB and 20 ns Gating

Abstract

A multipurpose monolithic array of 2×2 multi-channel digital silicon photomultipliers (MD-SiPMs) fabricated in 40nm CMOS technology is presented. Each MD-SiPM comprises 64×64 smart pixels connected to 128 low-power 45ps sliding-scale time-to-digital converters (TDCs). The MD-SiPMs are designed to indirectly capture gamma events in positron emission tomography (PET). The sensor can operate in frame-based and event-driven mode; the latter best suited to capture gamma events. The digital read-out is fully embedded in the sensor and it is reconfigurable by way of serial communication. Data packets are sent following a simple protocol compatible with an external FIFO, therefore eliminating the need of an FPGA. A dedicated input can be used to operate synchronously with an event generator, such as a pulsed laser, useful in other applications, like LiDAR. The system is inherently compatible with 3D-stacking technology; thus serving as a front end for different SPAD technologies, suitable for a variety of applications.