The MUX64 ASIC is a 64 -to -1 analog multiplexer to accommodate 64 inputs, with one addressed to output for ADC readout. It is developed for monitoring of the Low -Gain Avalanche Detectors (LGAD) detector modules in the High Granularity Timing Detector (HGTD) of the ATLAS Phase -II upgrade. The MUX64 chips will be used in the radiation field of high -luminosity pp collisions at LHC to an integrated luminosity of 4000 fb-1. This work presents the radiation tolerance study for the MUX64 being tested with 80 MeV protons and X-ray exposures for damages caused by Non -Ionizing Energy Loss (NIEL) and Total Ionizing Dose (TID), respectively. The irradiated samples demonstrated tolerance to the NIEL to a fluence of 3.21x1015 (Si, 1 MeV) neq/cm2, and the TID of 7.46x105 Gy (Si).

We present the design and the performance of MUX64, a 64-to-1 analogue multiplexer ASIC for the ATLAS High Granularity Timing Detector (HGTD). The MUX64 transmits one of its 64 inputs selected by six address lines for the voltages or temperatures being monitored to an lpGBT ADC channel. The prototype ASICs fabricated in TSMC 130 nm CMOS technology were prepared in wire-bonding and QFN88 packaging format. A total of 280 chips was examined for functionality and quality assurance. The accelerated aging test conducted at 85 degrees celsius shows negligible degradation over 16 days.