Avoiding PCB Crosstalk

Now that it is relatively cheap and easy to create a PCB, it is a common occurrence for them to be used in projects. However, there are a lot of subtleties to creating high-performance boards that don’t show up so much on your 555 LED blinker. [Robert Feranec] is well-versed in board layout and he recently highlighted an animation on signal crosstalk with [Eric Bogatin] from Teledyne LeCroy. If you want a good understanding of crosstalk and how to combat it, you’ll want to see [Eric’s] presentation in the video below.

Simplifying matters, the heart of the problem lies in running traces close together so that the magnetic fields from one intersect the other. The math is hairy, but [Eric] talks about simple ways to model the system which may not be exact, but will be close enough for practical designs.

The models use inductors and capacitance to represent different modes of crosstalk, and it’s likely you already know how to deal with those quantities. The video shows some simulations and also suggests methods to control the problem.

Even though the topic is PC boards, some of the same ideas apply to cables. Ethernet cables, for example, have specifications for FEXT for similar reasons.

Our own [Bil Herd] has a take on similar topics you might enjoy. [Feranec] is behind Fedevel Academy which we’ve read reviews about before.