NASA's space-based observatories, flyby spacecraft, orbiters, landers, and robotic and sample-return missions require robust command and control capabilities that can operate without elaborate environmental protection housing under extreme environments. Prixarc aims to develop and commercialize a custom application-specific integrated circuit (ASIC)-based 64-channel Time to Digital Converter (TDC) with 6 ps timing precision, radiation hardness to 1 Mrad (Si) and operational temperature range from −150 oC to +125 oC for NASA planetary missions. In this work, the development of mixed-signal data converter ASICs to operate at low and near cryogenic temperatures is an important contribution and novelty. Mixed-signal structured ASIC architectures are relevant to increasing science return and lowering costs for missions across all Science Mission Directorate (SMD) divisions. The proposed TDC with high time precision, high radiation hardness, and high channel count is possible because of two novel aspects: (i) stochastic TDC design, and (ii) a specialized fully depleted silicon-on-insulator (FDSOI) complementary metal–oxide–semiconductor (CMOS) fabrication process (28 nm FDSOI CMOS process from ST Microelectronics).
A TDC measures the time interval between start and stop pulses from the amplifier/discriminators connected to detectors. For example, the Cassini Plasma Spectrometer (CAPS) included an ion mass spectrometer (IMS) that provided species-resolved measurements of the flux of positively charged atomic and molecular ions as a function of energy/charge versus aperture entry direction. The time-of-flight spectrometer in the IMS utilized TDCs.
TDCs are used in many fields such as Positron Emission Tomography (PET), LIDAR optical time-of-flight measurements, high-energy nuclear physics detector interfaces, digital phase lock-loops (PLLs), and photonic integrated circuits (PICs). The detector electronics of space telescopes, e.g. James Webb Space Telescope operate at low temperatures where the proposed circuits are useful.