Relative Propagation Delay - The Best Tool for Length Matching
Creating a match group will make those nets a candidate for length matching. Differential pairs and single ended traces can
become part of a match group. Once a group is established, it is trivial to select or highlight the group as a unit. Then a single
entry will allow us to set a rule for the entire group.
Figure 6. Creating a match group involves selecting the nets and using the right mouse click to create the group in the Relative Propagation
Delay window or other electrical net assignment option. Here, we are creating a group of three nets which will be labeled I2C.
Creating the match group allows us to limit any deviations according to the specification. There isn't a maximum length for
I2C but I added one along with the relative propagation delay which is also arbitrary. The goal is to show two meters on a
trace meander in progress. With relative delay, the bounds are set by a single trace length for the others to match.
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Controlling Trace Length for Digital Circuits Using OrCAD X and Allegro X Tools
