A readout chip for spectroscopic X-ray imaging in photon-counting pixel detector

A pixel detector readout chip with multiple energy bins was designed for X-ray imaging applications. This chip was developed in a 0.11 µm CMOS technology. The active area on this chip consists of a matrix of 8 × 112 square pixels with 110 µm side. Each pixel unit was implemented with four programmable digital energy thresholds, which permits spectroscopic imaging in photon-counting pixel detectors. The deposited energy is measured with Time-over-Threshold method and a 5-bit clock cycle counter in the digital domain. Each energy bin has a 12 binary bit counter for recording the number of incident photons. Imaging quality degradation caused by charge sharing effect has been addressed by means of a digital in-pixel correction algorithm, which allows inter-pixel communication and can allocate the hit to the pixel with largest charge deposit. The design of this readout chip is presented in this paper.