4. You should already have values populated for the other parameters. Now apply the constraint set to any relevant diff
pairs by going to the worksheet Electrical > Net > Differential Pair.
5. Choose the ECS1 Constraint Set we recently made and apply it to any differential pair, say to the DP_DATA1 diff pair.
6. Then the values will appear on the relevant columns (see below).
7. Notice that from the analysis (you can right click the DP_DATA1 field then choose Analyze) that our traces are within
target tolerances.
Meaning of the Parameters:
Implement specific rules for differential pairs to ensure optimal signal propagation. This includes:
f
Dynamic phase tolerance: Allow for slight variations in differential pair length matching to account for manufacturing
tolerances. Ensuring that this remains as close to 0 as possible, reduces the common mode voltage that can be created by
slightly mismatched signals - intra pair skew.
f
Static phase control: Set strict length matching requirements to minimize skew between the positive and negative signals.
Some signals do not have to be matched instantaneously, but their data must arrive at the receiver at the same time.
f
Maximum uncoupled length: Specify the maximum length that differential pair traces can be routed separately before
recoupling. Being uncoupled allows for the introduction of unevenly distributed noise among diff pair traces, which can
cause the differential receiver to have a harder time canceling the signal noise.
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OrCAD X High-Speed Digital Design Guide
