Using Differential Pairs in Allegro PCB Editor
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Examples
Differential Pair Spacing
For maintaining a larger line-to-line spacing between differential pair objects to other
nets as compared to differential pairs to differential pairs, a spacing constraint could be
created and assigned. This example shows how to set up differential pairs in Constraint
Manager, so they are spaced 20 mils from other nets. Specific line-to-line spacing is
maintained between objects of differential pairs.
Assume that you have a requirement that differential pairs (DP) must have 20 mils
spacing between each DP object and any other non-DP net, while the spacing between
all non-DP nets is 5 mils.
To accomplish this task, refer to the database. It can be found in the 'Attachments'
section below the PDF. This pdf can be searched with the title on
https://support.cadence.com.
dp_16_space1.brd has been already set up with the required constraints. The
dp_16_stripped1.brd board is the same board but does not have the constraints. This
board can be used with the following information.
Procedure to follow (assuming DPs are already set up):
1. Create an ECSet that will contain the DP settings.
a. In the ELECTRICAL domain of Constraint Manager, select the Electrical
Constraint Set > Routing > Differential
Pair worksheet.
b. Right-click on the design name object and choose Create > Electrical
CSet from the menu.
c. Enter a meaningful name (for example, DP_10) and click OK.
d. Enter the DP electrical constraints (you may need to click on the "+" sign to
expand the rows).
Note: Repeat steps b-d for additional constraints with different values.
