A Fast, Low-Jitter, and Low-Time-Walk Multi-Channel Front-End IC for Diamond and Silicon Radiation Detectors

This article presents the design and implementation of a radiation-hardened analog front-end (AFE) integrated circuit (IC) developed for interfacing with solid state ionizing radiation detectors, providing accurate amplitude and time-of-arrival measurements. The AFE is designed for use in the Beam Conditions Monitor Prime (BCM’) of the ATLAS experiment at the Large Hadron Collider (LHC). The proposed AFE is comprised of four channels, allowing for re-configuration to operate as either a low-noise high-gain amplifier for beam luminosity measurements or a high-linearity low-gain amplifier for beam abort functionality. Each of the AFE channels consists of a low-noise trans-impedance amplifier (TIA) optimized for minimal jitter and amplitude noise, a second-stage differential amplifier, followed by a fully differential constant fraction discriminator (CFD) to provide an amplitude independent time pick-off with a wide dynamic range. The CFD utilizes a new all-pass filter delay topology and high-performance zero-crossing detector (ZCD) to minimize time-walk. The core of each AFE channel occupies an area of 0.06 mm
²
in a 65 nm CMOS technology and consumes 57 mW, including the drivers. The measured AFE chips achieve 1 ns pulse rise time, 130 electron baseline equivalent noise charge (ENC), and <25 ps root mean square (rms) jitter at 1 fC input charge. To the authors’ best knowledge, this work demonstrates the lowest published time-walk of ±6 ps across 30 dB signal dynamic range. Furthermore, irradiated AFEs are shown to tolerate up to 225 Mrad total ionizing dose with no significant degradation in measured performance characteristics.