The design and test results of A Giga-Bit Cable Receiver (GBCR) for the ATLAS Inner Tracker Pixel Detector

TL;DR

This paper reports on the design and testing of a high-speed ASIC for the ATLAS detector upgrade, demonstrating reliable data reception at 1.28 Gbps with low error rates and improved radiation immunity.

Contribution

Introduction of a new Giga-Bit Cable Receiver ASIC (GBCR) with enhanced radiation tolerance and lower jitter for the HL-LHC upgrade.

Findings

No Single-Event Upset observed in tests.

Bit error rate below 8*10^(-16), meeting criteria.

GBCR3 shows reduced jitter and improved radiation immunity.

Abstract

This paper presents the design and test results of a Gigabit Cable Receiver ASIC called GBCR for the HL-LHC upgrade of the ATLAS Inner Tracker (ITk) pixel detector. Three prototypes (GBCR1, GBCR2, and GBCR3) have been designed in the CERN-identified 65 nm CMOS technology. GBCR receives seven (GBCR2) or six (GBCR3) channels (RX) each at 1.28 Gbps from the front-end readout chip RD53B via flex cables up to 1 meter and Twinax cables up to 5 meters and sends the equalized and retimed signals to lpGBT. Both GBCR2 and GBCR3 ASICs have two transmitting channels (TX) that pre-emphasize the signals from lpGBT before sending them to RD53B through the same cables. No Single-Event Upset (SEU) is observed in any tested channels of GBCR2 in a 400 MeV proton beam. The extrapolated bit error rate for the future HL-LHC application is below 8*10^(-16), significantly below the specified BER criterion. GBCR3 is designed to improve the immunity to single-event-upset by applying the Triple Modular Redundancy (TMR) technology to all RX channels. The retimed signals from GBCR3 have less total jitter than those from GBCR2 (35 ps versus 79 ps). Each receiver channel of GBCR3 consumes 75% more power than that of GBCR2.