EMI-induced Delays In Digital Circuits: Prediction

A simple model is introduced to predict the changes in propagation delay in a logic inverter caused by low-level radio frequency interference. The change in delay is computed as a function of the induced voltage disturbance, which in turn can be computed from the incident field using linear frequency domain analysis. The model accounts for the dependence of the induced delay on the phase and amplitude of the RFI signal as well as on the slew rate of the logic transitions. Its predictions are shown to be in good agreement with experimental results and Spice simulations for interference frequencies up to the maximum switching frequency of the inverter (in-band interference).