Research on Automatic Measurement of Impulse Electromagnetic Noise (V) : Digital Circuit Model to Predict Spectra of Electromagnetic Radiation Noise

A simplified equivalent circuit model of a digital printed circuit including CMOS ICs is proposed. To predict a spectral peak profile of electromagnetic radiation noise from an IC package, a simple and rapid method is described. A digital circuit, considered as a RF circuit, has resonance owing to inductances of package pins and internal capacitances of digital gates. The resonance frequencies and the Q factors, which can be caluculated with the model, dominate the spectral peak profile of electromagnetic radiation noise. The caluculated resonance frequencies of some typical circuits, constructed by DIP or SOP ICs, agree with the measured peak frequencies within errors of 10 MHz