Crosstalk due to Capacitive coupling

Capacitive Coupling or Crosstalk Let us now assume traces running in parallel, one on the top of another. In this structure, we can think of the two traces forming a parallel plate capacitor. In other words you can think of the two traces connected by a capacitor in between them. Any AC signal in one trace will induce voltage in the nearby trace coupled capacitively.

How to avoid capacitive Coupling

Adjacent traces on the same layer, even if very close by, are less likely to have capacitive coupling as there is less capacitance formed by the two traces because of the small common area.

If there is a problem due to the capacitive coupling of the traces on the same layer, we can reduce it by increasing the separation between the traces and by reducing the length for which they run in parallel.

Capacitive coupling on adjacent layers is avoided by following simple rule of routing in horizontal and vertical directions on adjacent layers. In cases where it is not possible to follow this rule, attempt should be made to ensure that the traces are not exactly one on the top of another. We should also identify the traces that have high edge rate and that are more susceptible to noise. Attempt should be made to ensure that all the critical nets follow the design rule.


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