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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\gamma $</tex></formula> -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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$0.35 - \mu \hbox{m}$</tex> </formula> mixed-signal CMOS technology, the die size of the prototype chip is <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$2.2~\hbox{mm} \times 4.8~\hbox{mm}$</tex></formula> . At room temperature, the equivalent noise level of a typical channel reaches <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$133~\hbox{e}^ - ({\rm rms})$</tex></formula> 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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \pm 2\% $</tex> </formula> and the input energy dynamic range of the readout ASIC is from 10 keV to 1 MeV. The crosstalk between the channels is less than 0.4%. By connecting the readout ASIC to a CdZnTe detector, we obtained a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\gamma $</tex></formula> -ray spectrum, the energy resolution is 1.8% at the 662-keV line of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{137}{\rm Cs}$</tex></formula> source.