ALTAIR: A Low-Noise, Low-Power, High-Speed and Wide Dynamic Range ASIC for X- and γ-Ray Spectroscopy With CdTe/CdZnTe Pixel Detectors

ALTAIR is an application-specific integrated circuit (ASIC) developed for the readout of CdTe/CdZnTe detectors for X-gamma-ray spectroscopic imaging. ALTAIR is composed of 16 channels with analog and mixed-signal sections specifically designed for high energy resolution and high-rate applications with the constraints of a low power consumption and operation at room temperature. The ASIC has three selectable ranges for input charge signals covering photon energies up to 90, 160, or 300 keV, which allow to optimize the signal-to-noise ratio under different experimental conditions. Eight peaking times of the pulse shaper are selectable from 200 up to 2.3 mu s. ALTAIR includes a 180 bits register and an integrated serial peripheral interface (SPI) interface to configure the signal-processing parameters globally or independently for each channel. The power consumption is 950 mu W/channel or 1.35 mW/channel for single-ended or differential output versions, respectively. A minimum equivalent noise charge (ENC) of 37 electrons rms [386 eV full-width at half-maximum (FWHM) in CdTe] has been measured at 500 ns peaking time and 90-keV energy range. With a CdTe pixel detector connected to ALTAIR and operated at +24 degrees C, a pulser FWHM of 1.7 keV (160 el. rms) and 1.9-keV FWHM on 59.54 keV line of Am-241 have been achieved at a peaking time of 500 ns.