Allegro – Tip of the week: Looking for tighter coupling of differential traces at gathering location

While routing differential pairs, there is always an issue at round pins or vias. Users often want to have a better coupling between the traces by reducing the uncoupled distance.

There is a variable, padentry_factor, which you can use for this purpose. This variable helps specify a percentage value to control gathering for traces exiting a round pin or via while concurrently routing more than one net, such as a differential pair.

The purpose is to let traces gather sooner. The value is used as a percentage to reduce the minimum clearance that the gathering code requires between the pin/via and the second segment of the cline exiting the pad. By default, it requires 100 percent of the applicable minimum segment to pin/via spacing constraint. A value of 75 causes the minimum space to be 75 percent of the constraint set value.

The value for this variable can be set from Setup > User Preferences > Route > Connect.

Hope you found this useful. What are the other ways you follow to get a better coupling of differential pairs with longer lengths?