HEXID2: A Low-Power, Low-Noise Pixel Readout ASIC for Hyperspectral Energy-Resolving X-Ray Imaging Detectors

Abstract

We present a low-power, low-noise prototype pixel readout application specific integrated circuit (ASIC) for hyperspectral enegy-resolving X-ray imaging detectors. The ASIC provides 16-by-16 channels to read out positive and negative charges from 16-by-16 heagonal silicon or CZT detector arrays, at a pitch size of $250 \mu \mathrm{m}$, to achieve good spatial resolution and the ability to record the energy of a detected photon as well as its position. The readout is done by bumpbonding the anodes to the inputs of the ASIC. Each channel of the ASIC provides low-noise charge amplification, high-order shaping with baseline stabilization, discrimination, extraction of amplitude (with neighbour channels), multiplexing, and dissipates $\sim0.6$ mW. A smart readout of the triggered pixel and its adjacent six pixels in the hexagonal configuration allows reconstruction of events with charge sharing correction, and can be used to estimate the depth of the photon interaction and to suppress background events. The target equivalent noise charge (ENC) is $\sim10$ electrons for silicon detector pixel and $\sim15$ electrons for CZT detector pixel.