Cross talk in VLSI
What is Cross talk ?
Cross talk in VLSI (Very Large Scale Integration) refers to the unintended electrical coupling between two or more signals in an integrated circuit.
 |
| Coupling C between Wire1 and Wire2 |
This can result in degradation of the signal quality, such as a reduction in signal-to-noise ratio or even a change in the timing of a signal.
Cross talk can be caused by a number of factors, including the proximity of signal lines, mutual inductance and capacitance.
Visualizing Cross talk
Try to visualise what will happen to a static signal (0.5V) on wire2 when wire1 switches from lets say, 0V to 1V.
The signal (0.5V) on wire2 will change momentarily because of change in wire1 beside it, this is called cross talk. One wire is affecting other wire.
Well for your ease of understanding, I simulated a simple circuit with and without parasitic cap between two wires :
Without Cap between Wires :
Observed ?? the diffffference ! NOICE.
(I have inserted a very big cap though, 1mF, so that cross talk effect is visible in waveforms clearly)
How to reduce Cross talk ?
Designers use various techniques to minimize cross talk, such as:- Increasing the spacing between signal lines
Increasing the distance will decrease the coupling cap between the two wires. - Adding shielding
Adding a shielding line (generally connected to Ground) in between the two wires will remove direct coupling between Wire1 and Wire2.
Can you draw a diagram with a shield line between the two wires and visualise how does it help to reduce cross talk, if yes, Good! if no text me here - Changing the routing of signals
In this method the metal layers for routing the signals is made different which in turn reduces or removes coupling between the two wires.
Here is a funny meme on Cross talk, hit a like if you understood 😄
