A 30-ns recovery time, 11.5-nC input charge range, 16-channel read-out ASIC for PET application

This paper presents a read-out chip for Silicon Photomultipliers (SiPMs) targeting Positron Emission Tomography (PET) application. The ASIC contains 16 channels, each consisting of a current buffer, a charge sensitive amplifier, a digital validation block, a 10-bit ADC and a 12-bit TDC with 45-ps resolution. The ASIC was realized in a 0.15μm CMOS technology, and has a size of 2.8×2.2 mm2. The high input charge range (11.5nC) was designed for a wide range of SiPM cell gain and size, from 15μm to 50μm, and for a maximum input current of 20mA per channel. The proposed double-trigger event validation allows setting the triggering threshold at a very low level, for optimal photon arrival time statistics in the scintillation light readout. Also the recovery time in each channel is reduced down to 30ns. Characterization results with a 511keV gamma source show an energy resolution of 11.2% with 3×3mm2 SiPMs coupled to 3×3×5mm3 LYSO scintillator and coincidence timing resolution of 663ps