Design and characterization of CMOS multichannel front-end electronics for silicon photomultipliers

CMOS multichannel front-end electronics suitable for Silicon Photomultiplier detectors has been developed, mainly intended for medical imaging applications. The architecture of the analog channel, DC coupled to the detector, is based on a full current-mode approach, which allows to achieve a wide input dynamic range of about 70 pC while retaining very fast self-triggering capabilities. An 8-channel ASIC with on-chip ADC and a 32-channel prototype have been designed and manufactured, both featuring serial and sparse readout capabilities and a fast-OR circuit, able to generate a high-speed trigger signal from the discriminator outputs of the analog channels. Measurements obtained by coupling the 8-channel prototypes to an injection capacitance have been carried out for characterization purposes. The circuit has been also used to read-out SiPMs coupled to different kinds of light sources, such as a blue LED and a small LYSO scintillation crystal excited by gamma photons with different energies. The results obtained from these tests are presented and discussed, confirming the effectiveness of the proposed front-end architecture.