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

Abstract

This paper compares the EMC performance of three different voltage regulator 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 harmonic disturbance. The DPI immunity parameters were measured and recorded in real-time for an incident power between −13 and +30 dBm, while the ICs were exposed to low and high environmental stress conditions. It was found that the minimum injected power required to reach the defined failure threshold voltage criterion (+0.20 V) varied over frequency depending on the IC reference. Results demonstrated that the L78L05 IC reference was more immune to harmonic disturbance up to around 100 MHz compared to other identical IC references under nominal conditions, but its susceptibility to the EM interference increased above 600 MHz. Moreover, these functionally identical ICs showed significant evolution of their conducted immunity at all considered temperatures, depending on their manufacturer. The outcome of the DPI characterization on these IC references at both low and high thermal stress conditions irrespective of their manufacturers of clearly showed that the DPI immunity improves significantly with increasing frequency compared to that of nominal temperature, with little dispersion on minimum injected power needed to observe failure above 700 MHz. Input impedance curves were plotted at low, high and nominal temperature showed noticeable decline at high frequency, which could also explain the combined impact of temperature and obsolescence on the EMC performance of ICs selected from different manufacturers. Consequently, 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 IC references. The immunity behaviour of these ICs were further investigated by generating look up table data from the DPI measurements at nominal temperature.

Degradation and Reliability Modeling of EM Robustness of Voltage Regulators Based on ADT: An Approach and a Case Study

“…The DPI measurement setup is similar to that presented in [34] is implemented with the measurement algorithm shown in Fig. 4b.…”