# Ways to determine approximate magnitude of crosstalk between PCB layers

Is there any basic methods to calculate crosstalk between different layers in a multilayer PCB. I am not after anything exact just a way to grasp the magnitude of the issue.

The situation I am trying to solve is in a 4 layer space constrained PCB with a stackup of Signal-Ground-Power-Signal, on my bottom layer I have a number of differential +/- 10V Signals max freq 1KHz. On the power layer above these traces I have a power trace with a current varying between 0-200mA with a minimum rise time of approximately 0.1ms, the trace for the return current is directly adjacent.

Assuming there is no other way I can route my PCB how can I go about getting a feel for what kind of affect a step in my current can affect my signals.

Other data

Signal Output impedance <100 ohms

• Signal Input impedance approx 10k ohms
• Signal trace width 12mil, trace separation 12mil
• Power trace width 40mil, separation 20mill
• Copper Weight 1oz
• Outer plane separation 0.2mm
• Inner plane separation 1.2mm
• Length of parallel run 75mm
• check out the PCB Toolkit by Saturn PCB Design Inc. Commented Mar 1, 2016 at 6:38
• Why have I never run across this tool before, it looks pretty cool, any recommendations how I can get it to work for my stackup which is effectively two signals above a ground plane. Commented Mar 1, 2016 at 6:50
• So are you saying you've got a current-carrying pair on the 'power'-inner layer, and a signal diff-pair on the bottom layer, and they're both running parallel to each other for 75mm? But what's the lateral separation between them? Commented Mar 1, 2016 at 7:46
• On top of each other I know it's bad that's why I am trying to evaluate this vs running wires. Commented Mar 1, 2016 at 11:36
• I recommend Hyperlynx SI, though it is very expensive software there is a trial version. mentor.com/pcb/hyperlynx/signal-integrity Commented Mar 1, 2016 at 13:22