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What's Good About Allegro Widths & Gaps & Diff Pairs? Oh My – Check Out SPB16.3!

Comments(8)Filed under: PCB Layout and routing, PCB design, SPB, Differential Pair Support, Allegro PCB Editor, Allegro, PCB Editor, SPB 16.3, Allegro 16.3, layout, "PCB design", SPB16.3, design, differential pairs, diff pairs, gaps, widths

The SPB16.3 release of Allegro PCB Editor now provides the ability to resize line width and gap of differential pairs. Designers are faced with challenges driven by time, cost and quality. A change request can come from the electrical engineers that mandates that differential pair gaps and widths be resized. This can entail hours to hundreds of hours ripping up and rerouting entire sections of the design to the new constraints.

New in SPB16.3 is the Resize/Respace Diff Pair command resize_respace_dp (Route — Resize/Respace — Diff Pairs) which is available in the pre-selection and legacy mode. You select the differential nets in the canvas that are targeted for change, and a dialog box appears listing (by layer) the current line width and gap of the selected pairs. Adjacent to each entry are fields for you to enter in the replacement values for width and gap.

The process flow assumes that the change of the line width and gap precedes any constraint updates to the database. Once the physical changes are implemented, you should update the constraints in Constraint Manager and then update the DRCs to ensure that the gaps and widths are consistent with the constraints.

Read on for more details …

Using the command

To resize/respace the differential pairs in the design you use the following flow:
1.    In pre-select mode select the differential pairs you need to change. You can select one or more differential pairs that need to be changed. If you are in the legacy mode you enter the command and then select the differential pairs you want to change.
2.    Enter the command resize_respace_dp (Route — Resize/Respace — Diff Pairs).
3.    The User Interface appears listing all of the respective line widths and gaps of the selection set.

4.    Complete any changes needed. If there are multiple entries for a line width and gap -- for example the 3 rows for Current Width and Current Gap with values of 6.00 for the 3 separate layers (Top, Signal_3, Signal_6) as shown above -- and you make a change to one of the parameters, you are able to then copy that new parameter. A prompt will ask if you want to copy the new parameter to all layers that had the old parameter.

5.    Select "OK" to accept all of the changes. After the design updates expect to see uncoupling and spacing DRCs. It's the responsibility of the designer to synchronize the constraint system as well as clean up any route violations to other obstacles.

Note: The availability of this command will be from the Early Adopter category variable -- resize_respace_dp

Please share your experiences with this new feature!

Jerry "GenPart" Grzenia


By DIMA ALZOUBAIDI on December 28, 2010
Is there a demo version or free trial for Allegro 16.3?

By Tauni1959 on January 3, 2011
Hey Jerry, your becoming quite an Allegro Guru :-)

By Jerry GenPart on January 3, 2011
Hi Tauni!
Well... not really - as you know, there are expert Support AEs who provide me with the Allegro PCB Editor details.

By Jerry GenPart on January 3, 2011
Hi Dima -

You can check with our VAR - EMA Design Automation, at http://www.ema-eda.com if a demo version is available.


By Les on March 15, 2011
What hotfix version do you need ?

I don't see the diff_pair pulldown.

By Jerry GenPart on March 15, 2011
Hi Les,

This should be available in the base release - no HotFix is needed. However, per the Note in the Blog post -

Note: The availability of this command will be from the Early Adopter category variable -- resize_respace_dp. In Allegro PCB Editor, select Setup> User Preferences... Click the Early Adopter folder (on the left side tree). Check the box to the right of the resize_respace_dp Preference. Now, you should be able to either enter the command resize_respace_dp or see the menu option Route — Resize/Respace — Diff Pairs.

Finally, you need at least the Allegro PCB Design XL license (this is not available with the Allegro PCB Design L license).


By Kyle Tripician on March 24, 2011
Hi Jerry, I'm getting the error "Selected item not valid for current operation, ignored:..." it's a differential pair, so I don't know why I'm getting this error. Any ideas?

By Jerry GenPart on March 24, 2011
Hi Kyle,
I'd suggest you contact our Customer Support team - an Allegro PCB Editor AE would be best to discuss this with you.

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