Reliable study of digital IC circuits with margin voltage among variable DC power supply, electromagnetic interference and conducting wire antenna

摘要

This paper measures the margin voltage of a digital IC circuit in order to assess the deterioration of the margin voltage caused by variations in the DC power supply, electromagnetic interference (EMI), and the corresponding power induced in a conducting wire antenna (CWA). The present results confirm that these factors may influence the margin voltage to such an extent that the operation of the digital IC circuit may fail. This paper provides a theoretical analysis of the influence of these factors upon the margin voltage, and develops corresponding equations, which are then applied with appropriate parameter values to determine an optimal circuit operation. It is shown that the deteriorated margin voltage of the IC circuit is a function of the amplitude and frequency of the EMI source, and of the parasitic capacitance of the device, i.e. the greater the EMI amplitude and frequency, and the higher the capacitance of the device, the greater the likelihood that its operation will fail when subjected to a variable DC supply voltage, or to EMI and CWA effects. Furthermore, in the case of EMI, it is shown that an increased interference frequency will reduce the margin voltage of the device. Finally, it is noted that the smaller the input impedance of the IC device, the greater the influence of EMI is likely to be.