Design of a Multi-Channel Low-Noise Readout ASIC for CdZnTe-Based X-Ray and <formula formulatype="inline"><tex Notation="TeX">$\gamma $</tex></formula>-Ray Spectrum Analyzer

Abstract

In this paper, we report on the recent development of a 32-channel low-noise front-end readout ASIC for cadmium zinc telluride (CdZnTe) X-ray and $\gamma $ -ray detectors. Each readout channel includes a charge sensitive amplifier, a CR-RC shaping amplifier and an analog output buffer. The readout ASIC is implemented using TSMC $0.35 - \mu \hbox{m}$ mixed-signal CMOS technology, the die size of the prototype chip is $2.2~\hbox{mm} \times 4.8~\hbox{mm}$ . At room temperature, the equivalent noise level of a typical channel reaches $133~\hbox{e}^ - ({\rm rms})$ with the input parasitic capacitance of 0 pF for the average power consumption of 2.8 mW per channel. The linearity error is less than $ \pm 2\% $ and the input energy dynamic range of the readout ASIC is from 10 keV to 1 MeV. The crosstalk between the channels is less than 0.4%. By connecting the readout ASIC to a CdZnTe detector, we obtained a $\gamma $ -ray spectrum, the energy resolution is 1.8% at the 662-keV line of $^{137}{\rm Cs}$ source.