Combining Obsolescence and Temperature Stress to Evaluate the Immunity of Voltage Regulators to Direct Power Injection in Long-Lifespan Systems

This letter compares the electromagnetic compatibility (EMC) performance of three different voltage regulator integrated circuits (ICs) (i.e., UA78L05, L78L05, and MC78L05) developed by three different manufacturers, with similar functionality and pin compatibility, under the influence of low and high temperature stress conditions (i.e., −30 °C and +100 °C). Direct power injection (DPI) was performed on these ICs to analyze the impact of applying thermal stress on the conducted immunity to the injection of a single-tone RF disturbance signal. The DPI immunity parameters were measured and recorded in real time for an incident amplified power, while the ICs were exposed to low and high thermal stress conditions. It was demonstrated that the minimum injected power required to reach the defined failure threshold voltage criterion $(\pm 4$ %) varied over frequency depending on the ICs. Moreover, these functionally identical ICs showed significant evolution of their conducted immunity in all the considered temperatures, depending on their manufacturer. Input impedance curves were monitored at low, high, and nominal temperatures, showing a noticeable decline of impedance at high frequencies. Moreover, the equivalent $RLC$ values of the lumped elements (i.e., resistor, inductor, and capacitor) were extracted and compared at these aforementioned temperature conditions to model the power supply network impedance for the selected ICs. The immunity behavior of these ICs was further investigated by generating lookup table data from the DPI measurements.