.png)
CLICK THE PLAY BUTTON TO WATCH THE LESSON.
Action list:
In this lesson, I intend to discuss two significant considerations that arise when attempting to address EMC (Electromagnetic Compatibility) issues, particularly at high frequencies. Typically, the standard approach involves the use of bypass capacitors as a means of filtering signals. While this method is widely adopted, there are specific challenges that must be recognized to ensure its effectiveness.
One of the key factors to examine is related to the impedance profile of the capacitor. As we know, no electronic component behaves in an ideal manner; every component exhibits certain non-ideal characteristics in addition to its expected behavior. Capacitors are no exception to this rule. The way a capacitor performs at high frequencies depends on these non-ideal characteristics, which significantly influence its impedance profile.
It is a common misconception that the impedance of a capacitor is always purely capacitive. In practice, when analyzing capacitors in the context of frequency, a more complex behavior emerges.
Initially, the impedance is indeed capacitive. However, beyond the resonant frequency of the capacitor, it begins to exhibit inductive behavior. This shift in characteristics is critical to understand, as it can have adverse effects when the capacitor is used to mitigate EMC issues. Therefore, selecting capacitors based on their impedance profiles, as outlined in their datasheets, becomes an essential step in ensuring optimal performance.
When choosing a capacitor, it is particularly important to verify that the frequency range of interest, falls within the capacitive region of its impedance curve, rather than the inductive region or beyond. This consideration becomes even more significant when dealing with digital signals. Digital signals are not limited to a single frequency, but instead, they encompass a fundamental frequency along with numerous harmonic frequencies.