Noise limits of AToM, a128 channel CMOS readout chip in applications with room temperature high granularity detectors

AToM, a CMOS 128 channel signal processing chip, was originally designed fo r the readout of the microstrip Silicon Vertex Tracker in the BaBar experim ent at SLAG. Each channel in the chip includes an analog section, with low- noise preamplification, shaping, and A/D conversion. A digital section prov ides data buffering and formatting, and serial sparsified readout. The chip is able to process signals from both electron and hole collecting electrod es on a wide dynamic range. AToM is presently available in both rad-soft an d rad-hard implementations. This paper aims at showing that AToM has a much broader application perspective in association with room-temperature high- granularity detectors, for instance in X- and gamma-ray imaging and signal processing for focal plane detectors. The first step toward this extension is the analysis of the intrinsic noise and accuracy limitations in radiatio n energy measurements. For this purpose the analysis is focused on the nois e performances of the analog section, as a function of the detector capacit ance, and of the signal peaking time. The effect of series white and 1/f no ise and of parallel noise is studied to define the best operating condition s with different detector types. (C) 2001 Elsevier Science B.V. All rights reserved.