Abstract
Presented circuit, IDeF-X HD (Imaging Detector Front-end) is a member of the IDeF-X ASICs family for space applications. It has been optimized for a half millimeter pitch CdTe or CdZnTe pixelated detector arranged in 16×16 array. It is aimed to operate in the hard X-ray range from few keV up to 250keV or more. The ASIC has been realized in AMS 0.35μm CMOS process.The IDeF-X HD is a 32 channel analog front-end with self-triggering capability. The architecture of the analog channel includes a chain of charge sensitive amplifier with continuous reset system and non-stationary noise suppressor, adjustable gain stage, pole-zero cancellation stage, adjustable shaping time low pass filter, baseline holder and peak detector with discriminator. The power consumption of the IDeF-X HD is 800μW per channel. With the in-channel variable gain stage the nominal 250keV dynamic range of the ASIC can be extended up to 1MeV anticipating future applications using thick sensors. Measuring the noise performance without a detector at the input with minimized leakage current (programmable) at the input, we achieved ENC of 33 electrons rms at 10.7μs peak time. Measurements with CdTe detector show good energy resolution FWHM of 1.1keV at 60keV and 4.3keV at 662keV with detection threshold below 4keV. In addition, an absolute temperature sensor has been integrated with resolution of 1.5°C.
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