144 Channel measurement IC for CdZnTe sensors with energy and time resolution

A 144 channel measurement IC for CdZnTe detectors, used for PET, is presented. Each channel consists of a charge sensitive amplifier, a fast and a slow shaper, a peak sampler for the energy acquisition and an event detector based on a time to digital converter to generate an accurate time stamp for each event. The channels are multiplexed to a fast pipeline ADC on demand. Measurement results for the ASIC showed a noise equivalent input charge of 800 e− rms and a time resolution of 737 ps rms. Evaluation results with a CdZnTe detector yielded an energy resolution of 4.4% full width half maximum at 662 keV with a 137Cs radiation source. The IC is implemented on a 180 nm CMOS process with a total chip size of 100 mm2.