Via Stubs and Propagation Delay Script

Via Stubs and Delay - GUI

This Script can find Via Stubs and Set Via Propagation Delay times.

Enter the Max Stub length allowed in mils. 

Select Top or Bottom or both to find and select stubs.

Then select Run

For zero length stubs enter 0 in Max Stub, then select Run

Double Clicking Max Stub will set Max Stub = to 1/2 Board's Copper Height.

Via Propagation Delay Notes:

Select more or less than 1 Via to set the Propagation Delay of all Via Drill Pairs.
Select only one Via to set the Propagation Delay of all Via's in the same Drill Pair.

Click the Delay Button to update the Propagation Delay.

Note Altium calculates the delay as the proportion of the via the signal path between the start and stop layers, this is not the physical ength of the via. It is the signal path electrical length.

Example: A board with a total thickness of 61.8mil, including a total of 1mil of solder mask and 2mil outer Cu thickness, where the electrical via length is calculated as Total - Soldermask - 1/2 top Cu - 1/2 bot Cu = 58.8mil.  

Altium uses 1/2 of the copper height of the starting and stopping layers.

Example:

The Calculated Delay of the Via is 10.917pSec for a signal path length of 58.8mils.

Related Links:

Signal Integrity Characterization of Via Stubs on High-Speed DDR4 Channels | 2020-05-14 | Signal Integrity Journal

https://resources.altium.com/p/your-complete-guide-stub-analysis

For more inforamation about this script Contact Parts (Randy Clemmons)

That's it !

Supply Nets (Voltage = 0 . . .

To disable Auto Generate Supply Nets

Preferences > General > Advanced > Schematic.AutoGenerateSupplyNetsRule > Disable

Restart (Close and Open) Altium

See: https://forum.live.altium.com/#/posts/260254/848610

That's it !

Return Path Design Rules - DRC Gotchas

The Design Rule

Note:  

Most designs should NOT include Not inAnyDifferentialPair in the Scope as shown.

This is a special case for the board used in this Return Path DRC feature review.

The example Rule shown above is targeting a specific Net Class.

You might want to set the Scope to target All

Gotcha 1

In Gotcha 1 the problem is the GND Via on the left has a signal routed between the flagged via and the GND Via.

Solution 1: Add another Via or Waive the Violation

Other Points of Interest:

Per online help

Exclude small areas of copper from flagging a violation by setting the required value (in sq. mils, 10 by default) of the PCB.Rules.ReturnPathIgnoreArea option in the Advanced Settings dialog.

That's it !

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