STiC ? a mixed mode silicon photomultiplier readout ASIC for time-of-flight applications

STiC is an application specific integrated circuit (ASIC) for the readout of silicon photomultipliers. The chip has been designed to provide a very high timing resolution for time-of-flight applications in medical imaging and particle physics. It is dedicated in particular to the EndoToFPET-US project, which is developing an endoscopic PET detector combined with ultrasound imaging for early pancreas and prostate cancer detection. This PET system aims to provide a spatial resolution of 1mm and a time-of-flight resolution of 200ps FWHM. The analog frontend of STiC can use either a differential or single ended connection to the SiPM. The time and energy information of the detector signal is encoded into two time stamps. A special linearized time-over-threshold method is used to obtain a linear relation between the signal charge and the measured signal width, improving the energy resolution. The trigger signals are digitized by an integrated TDC module with a resolution of less than 20ps. The TDC data is stored in an internal memory and transfered over a 160MBit/s serial link using 8/10bit encoding. First coincidence measurements using a 3.1 x 3.1 x 15mm(3) LYSO crystal and a S10362-33-50 Hamamtsu MPPC show a coincidence time resolution of less than 285ps. We present details on the chip design as well as first characterization measurements.