SPIROC (SiPM Integrated Read-Out Chip): dedicated very front-end electronics for an ILC prototype hadronic calorimeter with SiPM read-out

The SPIROC chip is a dedicated very front-end electronics for an ILC (International Linear Collider) prototype of hadronic calorimeter using Silicon photomultiplier (SiPM) or Multi-Pixel Photon Counters (MPPC) readout. This ASIC is due to equip a 10,000-channel demonstrator in 2010. SPIROC is an evolution of FLC-SiPM used for the ILC Analogue HCAL physics prototype. The first prototype of SPIROC was submitted in June 2007. It embeds cutting edge features that fulfil ILC final detector requirements. It has been realized in 0.35 μm SiGe technology. It has been developed to match the requirements of large dynamic range, low noise, low consumption, high precision and large number of readout channels needed. SPIROC is an auto-triggered, dual gain, 36-channel ASIC which allows to measure on each channel the charge from one photoelectron to 2,000 photoelectron and the time with a 100 ps accurate Time-to-digital Converter (TDC). An analogue memory array with a depth of 16 for each channel is used to store the time information and the charge measurement. A 12-bit Wilkinson Analogue-to-digital Converter (ADC) has been embedded to digitize the analogue memory content (time and charge on 2 gains). The data are then stored in a 4 Kbytes RAM. A very complex digital part has been integrated to manage all these features and to transfer the data to the DAQ which is described in Dulucq et al. After an exhaustive description, the extensive measurement results of this new front-end chip are presented.