Solar Intensity X-Ray Spectrometer (SIXS) ASIC onboard the ESA BepiColombo mission to Mercury

The new SIXS prototype ASIC has been designed for detecting and measuring solar X-rays in a Mercury orbit onboard BepiColombo. The SIXS detector consists of a CsI(Tl) core detector and 5 Silicon surface detectors. This new ASIC has undergone major modifications and has a new differential charge preamplifier without any pole zero cancellation and has a large dynamic range of 2,000e- to 1,500,000e-. The ASIC has 8 channels, each of which consists of a preamplifier, a CR-RC shaper, a peak detect hold, a comparator, a buffer, and a new 8 bit resistor string DAC which sets the programmable threshold for the comparator There are 6 channels for Si detectors with a shaping time of 1μs and 2 channels for CsI detector with a shaping time of 3μs, one of which has twice the gain to accommodate for low output efficiency of the detector. The channels are multiplexed to a single 10/11 bit SAR ADC which runs at a 10MHz clock and additional on chip programmable phase shifted clocks and programmable Upper and Lower threshold voltages. This ASIC has been manufactured in a 0.35μm CMOS process using enclosed geometry transistors. All digital logic in the ASIC including control and ADC logic use voting logic flipflops for SEU prevention.