Performance of ALTIROC2 readout ASIC with LGADs for ATLAS HGTD picosecond MIP timing detector

Abstract

ALTIROC2 is a 225-channel ASIC designed in CMOS 130 nm to read out a 15 × 15 matrix of 1.3 mm × 1.3 mm Low Gain Avalanche Diodes (LGAD) for the ATLAS HGTD (High Granularity Timing Detector). The targeted combined time resolution of the sensor and its readout electronics range from 35 ps/hit (initial) to 65 ps/hit (end of operational lifetime). Each ASIC channel integrates a high-speed preamplifier followed by a high speed discriminator and two TDCs for Time-of-Arrival and Time-Over-Threshold measurements as well as a local memory. This front-end must exhibit a small jitter while keeping a challenging power consumption of less than 4.5 mW per channel. This conference proceeding summarizes the ASIC architecture, its measured performances compared to simulation, along with the requirements for the ATLAS HGTD experiments.