A Mixed-Signal ASIC for CdTe/CdZnTe Detectors Readout in Battery Powered Capsule for Colon 3D-Imaging

An Integrated Circuit (IC) for processing the signals from CdTe/CdZnTe X-ray detectors in the 5-100 keV energy range is presented. The IC, named CCA, is designed to operate in a capsule for colon 3D-imaging as a diagnostic tool for cancer prevention. The CCA is composed of a low-power consumption analog and a digital sections for counting photons within two energy windows to a maximum of 130 × 10 ³ photons per second. The analog section consists of a preamplifier optimized for detectors with 8 pF capacitance, a pulse shaper with 4 shaping times selectable between 0.5 μs and 2 μs, a peak stretcher and an analog buffer able to drive up to 15 pF load. The digital section is composed of a two energy windows discriminator fully configurable in the 8.5-120 keV range with 7 bits energy thresholds resolution, two 12 bits counters, two memory registers and an SPI interface for IC configuration and data transfer. The CCA guarantees stable spectroscopic-grade performance allowing for supply voltage variations between 3.1 V to 2.5 V, as is the case of the battery powered capsule during its operation; this feature has been achieved with no voltage regulator for power saving.