Design and Test of the CROCv1 Analog Front-End Processor for the CMS Pixel Readout at the HL-LHC

This paper briefly discusses the design and the main test results relevant to the analog front-end processor, referred to as the Linear front-end, integrated in the CROCv1 chip. CROCv1 is the full-scale ASIC (featuring an area close to 4 cm2) developed by the RD53 Collaboration for the pixel readout at the high-luminosity upgrade of the CMS experiment, and is expected to be the last stage before the submission of the production chip for the actual experiment. The chip includes a matrix of 432x336 analog front-end channels, each featuring a low-noise charge sensitive amplifier driving a current-mode comparator, which is exploited, together with a digital counter, for Time-over-Threshold conversion of the sensor signal. The test results discussed in the paper are focused on the main analog performance parameters of the Linear front-end, including noise, threshold dispersion and time-walk.