Abstract
A direct charge conversion LSI for photon counting X-ray imager has been fabricated by TSMC 0.18um CMOS process. This LSI is designed to prove a behavior of the direct charge conversion architecture based on charge injection [1] for photon counting with energy information. The LSI has charge-to-digital convertors (QDC) used to read out a charge generated by an X-ray detector such as CdTe and digitize energy information of the source X-ray photon. The QDC realizes 15 energy windows within 200 keV and the LSI provides two 12-bit memories to output two images with differential energy information simultaneously. The LSI has 1600 QDCs and its pixel pitch is 80um. Analogue behaviors of the QDC, characteristics of energy discrimination and a capability to take X-ray/gamma-ray images have been tested. As the results, a desired gain and good linearity are equipped on the QDC, spectra of 241Am and 57Co can be discriminated, and differences between with and without a material have been shown as image.
Published Version
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