Design of a Trigger Data Serializer ASIC for the Upgrade of the ATLAS Forward Muon Spectrometer

A small-strip thin gap chamber (sTGC) will be used for both triggering and precision tracking purposes in the upgrade of the ATLAS forward muon spectrometer. Both sTGC pad and strip detectors are read out by a trigger data serializer (TDS) application-specific integrated circuit (ASIC) in the trigger path. This ASIC has two operation modes to prepare trigger data from pad and strip detectors, respectively. The pad mode (pad TDS) collects the firing status for up to 104 pads from one detector layer and transmits the data at 4.8 Gbps to the pad trigger extractor every 25 ns. The pad trigger extractor collects pad-TDS data from eight detector layers and defines a region of interest (ROI) along the path of a muon candidate. Data defining the ROIs is returned to the strip TDS. In the strip mode (strip TDS), the deposited charges from up to 128 strips are buffered and time-stamped, and a trigger matching procedure is performed to read out strips underneath the ROI. The strip-TDS output is also transmitted at 4.8 Gbps to the following field-programmable gate array (FPGA) processing circuits. Details of ASIC design and test results are presented in this paper.