Silicon Photomultiplier integrated readout chip (SPIROC) for the ILC: Measurements and possible further development

The SPIROC chip is a dedicated very front-end ASIC chip for an ILC hadronic calorimeter technical prototype with Silicon Photomultiplier (or MPPC) readout. This ASIC is due to equip a 2,000-channel demonstrator in 2009. The SPIROC chip is the successor of the ILC SiPM ASIC presently used for the ILC AHCAL physics prototype, incorporating additional features like auto-triggering, pipelines, digitization as well as power pulsing. Realized in 0.35 ¿m SiGe technology, it is designed in order to fulfill ILC final detector requirements of large dynamic range, low noise, low power consumption, high precision and large channel numbers. The SPIROC is a 36-channel chip. Each channel has bi-gain amplification, auto-triggering capability, a 16-bit depth analog memory array and a 12-bit wilkinson ADC. It allows time and charge measurements at the same time with digitized data results. The digitization is controlled and read out by the digital part of the chip. After the submission in June 2007, extensive measurements have been carried out to characterize the chip. This chip has been proven to be successful in calorimeter calibration as well as real physics experiments. Besides of the affirming measurement results, possible improvements are proposed in order to make the chip even more versatile in dealing with a large variety of Silicon Photomultipliers.