A 65 nm CMOS Readout ASIC with Dynamic Signal Compression for Balloon-Borne Spectrometry Applications

Balloon-borne and spaceborne spectrometers require front-end electronics that achieve a wide dynamic range and high energy resolution while operating under strict thermal constraints. These systems must also minimize power consumption to comply with the limited onboard power budget available during flight. ANTARES4 is a prototype readout application-specific integrated circuit fabricated in a commercial 65 nm complementary metal-oxide-semiconductor process. The chip integrates eight fully analog channels, each comprising a charge-sensitive amplifier followed by a semi-Gaussian CR-RC shaper with selectable peaking times from 0.2 μs to 1.6 μs for signal-to-noise optimization. The charge-sensitive amplifier feedback capacitor is implemented using metal-oxide-semiconductor devices, enabling bilinear input-output behavior and dynamic signal compression with differentiated gain for low-energy X-rays and high-energy charged particles. Four feedback configurations, including both n-type and p-type metal-oxide-semiconductor capacitors with matched gate areas, have been implemented for direct comparison. The circuit operates at approximately 3.5 mW per channel, well within the target budget, and achieves simulated resolutions of 3.5 keV full width at half maximum for a detector capacitance of 40 pF. The input dynamic range extends over four decades, from 10 keV to 100 MeV. The chip has been submitted for fabrication, and a dedicated test board has been developed for forthcoming characterization at room temperature and down to −40 °C.