Understanding Crosstalk - Altium Academy

[@MathJohnsen]

Clearly conveyed! To reduce crosstalk; increase spacing S between signal lines or decrease height H to adjacent plane. One question though: what are the equations used to define the minimum S, given H and rise time, and vice versa the maximum H, given S and rise time? EDIT: I discovered the Saturn PCB Toolkit has a Crosstalk Calculator that helps me in this regard, but knowing the relations behind the calculator would be a very valuable insight.

[@Zachariah-Peterson]

There are no equations specifying minimum S or H values. These depend on the thickness of the available materials used to build the board (H value) and the minimum line spacing that can be etched during fabrication (S value). The rise time is also not controllable, it is something that is determined by the output buffer in the integrated circuit.

[@Ech01378]

Perfect explanation! Thanks a lot!

[@InfiniteCat]

What a guy! Nice explanation!

[@thenextproblem8001]

Awesome explanation. İ want to ask another, if the victim is digital signal line does it matter if the hot line is another signal or power line?

[@Zachariah-Peterson]

No it does not matter, crosstalk always occurs whenever there is switching action, what matters is the edge rate. This is why a relatively slowly changing waveform on the switching node in a switching regulator can exhibit as much or more noise as a very fast digital signal with low voltage level; the reason is that the dV/dt or dI/dt is responsible for crosstalk, and in switching regulators these derivatives can still be very large because you could be making large voltage/current transitions over time.

[@thenextproblem8001]

@@Zachariah-Peterson thanks for the explanation. What if we switch the relay? İ can't control the switching time here its just a click. İ placed the reversed diode. İ use optocoupler i even placed another bjt to control optocoupler but still crosstalking and random clicks occurs

[@Zachariah-Peterson]

​ @thenextproblem8001 Without seeing your PCB layout and schematic it is hard to say exactly. But with relays you can have a large derivatives (dV/dt or dI/dt) during switching especially if in a high voltage system. This is true even if the switch rate in the relay is slower than in a typical digital signal. These large derivatives are what create crosstalk, it does not matter if you look at power systems or digital designs. So if you route the victim line too close to the relay it could produce that switching noise on the victim line. One thing with relays is that they basically produce the same kind of noise as the switching node in a switching regulator, and the easiest way to prevent coupling from that node into a victim line is to keep ground near that switching node. Make sure the current loop through the relay is small and use large ground pours and that will probably help.

[@vitorracoski2874]

Awesome Video!

[@mjz-e9i]

nice class

[@alessandrolima4266]

Amazing

[@AltiumAcademy]

Thanks