Critical Trace Length
Definition: Critical trace length is the length of a trace or transmission line that would cause the signal to reflect if it's too long
electrically.
Steps:
1. Navigate to the Electrical > Routing > Total Etch Length worksheet.
2. We have existing Constraint Sets but feel free to make a new one.
3. For an electrical constraint set in the list, set the Maximum Total Etch. For example, USB 2.0 operating at 480 Mbps, may
consider any traces longer than 3500 mils (88.90 mm) to be electrically long. So we set the max total etch to that value
(shown below).
4. Recall that this is just the constraint set. It must be applied to nets in the design. Navigate to the Electrical > Net >
Routing > Total Etch Length worksheet.
5. Next right-click on the nets you want to analyze then choose Analyze. You will see the results below.
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OrCAD X High-Speed Digital Design Guide
