96-channel Time-to-Digital converter (TDC) for the RPC Phase-2 Link System

The phase-2 upgrade of the CMS RPC System for the low-eta region will enhance the electronics performance and muon hit time resolution to cope with the High Luminosity Large Hadron Collider (HL-LHC) conditions. In the Compact Muon Solenoid (CMS) experiment, Resistive Plate Chambers (RPC) have between 36 and 96 strips read out by frontend electronics boards (FEB). The FEB outputs are connected to the link system boards where 96-channel time-to-digital converters (TDC) implemented in a Kintex-7 Field Programmable Gate Array (FPGA) measure the arrival time of the muon hit at a fine-time resolution of 1.56 ns that is near to the RPC intrinsic time resolution. The results show that these TDCs have a linear transfer function with a sufficient time resolution, and the output data is ready after four bunch crossings.