Optical Link ASICs for the LHC Upgrade

TL;DR

This paper presents the design and testing of three radiation-hard ASICs in 130 nm CMOS for optical data transmission in the upgraded ATLAS pixel detector at the LHC, demonstrating robustness under high radiation doses.

Contribution

Introduction of three novel ASICs for optical links in LHC upgrades, optimized for radiation hardness using 130 nm CMOS technology.

Findings

ASICs functioned well after irradiation with minimal degradation

VCSEL driver showed some threshold shifts but remained operational

ASICs are suitable for high-radiation environments in particle physics experiments

Abstract

We have designed three ASICs for possible applications in the optical links of a new layer of pixel detector in the ATLAS experiment for the first phase of the LHC luminosity upgrade. The ASICs include a high-speed driver for the VCSEL, a receiver/decoder to decode the signal received at the PIN diode to extract the data and clock, and a clock multiplier to produce a higher frequency clock to serialize the data for transmission. These ASICs were designed using a 130 nm CMOS process to enhance the radiation-hardness. We have characterized the fabricated ASICs and the submission has been mostly successful. We irradiated the ASICs with 24 GeV/c protons at CERN to a dosage of 70 Mrad. We observed no significant degradation except the driver circuit in the VCSEL driver fabricated using the thick oxide process in order to provide sufficient voltage to drive a VCSEL. The degradation is due to a large threshold shifts in the PMOS transistors used.