PREDICTION OF DELAYS INDUCED BY IN-BAND RFI IN CMOS INVERTERS

Delays induced by radio frequency interference (RFI) in CMOS inverters are measured under radiated and capacitively coupled interference, Ex perimental and theoretical investigations of the effects of the RFI co upling mode (capacitive versus inductive) on the amount of induced del ay are presented and a worst-ease coupling mode is identified, A formu la to predict delays caused by in-band low-level RFI in CMOS inverters is introduced. This formula uses experimentally determined parameters which are dependent on the coupling mode, The change in delay is comp uted as a function of the induced voltage disturbance, which in turn c an be computed from the incident held using Linear frequency-domain an alysis, The formula accounts for the dependence of the induced delay o n the phase and amplitude of the RFI signal as well as on the slew rat e of the logic transitions, A delay growth phenomenon in a string of i nverters is identified and characterized, A correction to the delay pr ediction formula is proposed in order to take this growth into account in worst-case predictions.