Short-term Recovery Effect in a Power Integrated Circuit Exposed to X-Rays

During the previous examinations of a negative voltage regulator in various bremsstrahlung fields, a short-term recovery effect was perceived in some samples. In one set of bias and load conditions of the examined power integrated circuit, it was observed that the usual trend of (the absolute value of) the output voltage decline, perceived in all the other samples, was briefly violated. Thus, a slight recovery of the output voltage during irradiation was observed, followed by another drop in the output voltage, until the circuit shuts down. In the research presented, an effort has been made to model this effect using the previously developed SPICE micromodel of LM2990T-5.0 circuit. Radiation induced leakage currents have been simulated in critical transistors in the operational amplifier circuit, recreating the conditions prior to device failure after X-ray exposure.