cross talk and differential traces communication question

[yefj]

Hello ,When using differential signal communication, ,except that on the recieving side it eliminates why noise.
Why it also eliminates cross tal to the neighbors?
Thanks.

 

[barry]

If I understand your question, you want to know why differential signals eliminate noise and cross-talk?

Noise is eliminated because it appears on the differential pairs as common-mode. In other words, the same noise is on both traces (or wires). Since a differential receiver subtracts one signal from the other, the noise is subtracted.

 

[yefj]

yes,but what about cross talk?

 

[KlausST]

Hi,

Cross talk can be because of neighbouring signal lines.
Here the differential wiring makes no difference.

But cross talk can be because of GND bounce. Say you have two single ended signals. Each is referenced to GND.
Then send a signal to one line, it will cause GND current ... and with GND impedance it will cause GND bounce.
Since the other signal is referenced to the "bouncing" GND it looks like cross talk.

No back to differential signaling. Here you have very low HF GND current, thus less bounce.. and it looks like low cross talk.

Klaus

 

[FvM]

Crosstalk is effectively reduced for twisted pairs and equivalent structures.

 

[vfone]

The highest cross-talk coupling happen between two single-ended lines.
The minimum cross-talk happen when a differential line couple to another differential line.
When a single-ended line couple to a differential line, one trace of the pair is closer to the single-ended line, so that trace will couple more strongly and there will be a small differential coupling. The cross-talk in this case depends not only by the distance between single-ended and differential lines, but depends also by the spaicing between the differential traces.