Investigating Total Ionizing Dose Effect on LVDS Receivers with Impedance Spectroscopy

Low-Voltage Differential Signaling (LVDS) receivers are widely used in high-speed serial links in several environments with radiation, including nuclear and high-energy physics experiments, spacecraft and satellites, and medical physics. In this work, we studied Total Ionizing Dose (TID) effects induced by 60Co gamma rays on LVDS receivers (part number DS90LV048A, from Texas Instruments) exposed to a high dose of 15.4 kGy at a dose rate of 364 Gy/h. TID tests have been performed at the CERN CC60 facility, that hosts a ~ 3 TBq 60Co radioactive source. Radiation effects were studied using both conventional techniques, such as current and voltage monitoring during irradiation, waveform analysis, and bit error rate, and Impedance Spectroscopy (IS), a frequency-domain technique well established in electrochemistry but still underexplored in the field of radiation effects on electronics. Conventional analysis revealed no significant degradation in key performance metrics, including signal integrity, rise and fall times, amplitude, and common-mode voltage range. However, the proposed approach based on IS and I–V curve analysis enabled the observation of subtle TID effects. Equivalent circuit modeling based on two time-constant networks was employed to analyze specific device sections, including the power rail network, Electrostatic Discharge (ESD) protection circuit, input and output stages. In the power rail, IS identified a dominant time constant associated with a 96 pF lumped capacitance, whose value remained stable after irradiation. A second, slower time constant, attributed to charge trapping and detrapping mechanisms, showed a significant increase after radiation exposure. The ESD protection circuit, based on NPN avalanche breakdown, exhibited no change of its capacitance values due to TID, although a slight decrease in leakage resistance was observed. Moreover, IS revealed that the breakdown avalanche is triggered at around 5 kHz and, beyond this frequency, the circuit exhibits the behavior of a parallel RC network, with no shift in this frequency value observed after irradiation. In the input stage, IS measurements showed that the differential switching threshold remained within the 30–120 mV range, with current variations <15% after irradiation. The output driving capability exhibited a 6% reduction in the maximum sourcing current and a 4% increase in series output resistance. IS analysis also showed the presence of a lumped inductance of the order of magnitude of 1H in the output driving circuit that did not change after irradiation. However, IS revealed subtle changes in the device internal physical mechanisms that are not detectable through conventional methods. This study highlights IS as a valuable, non-destructive technique for assessing radiation effects in digital microelectronics.