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 Different Force and Sense Line Widths using Pin Pair Physical Constraints 

Last post Fri, Feb 4 2011 11:19 AM by Brando. 10 replies.
Started by jackg23 01 Feb 2011 03:48 PM. Topic has 10 replies and 3547 views
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  • Tue, Feb 1 2011 3:48 PM

    • jackg23
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    • Chandler, AZ
    • Posts 2
    • Points 40
    Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply
    Hi all,

    I have been trying to find a method to specify different line widths for the same net. Specifically, I need a force line and sense line to be routed separately to single DuT pin. These lines should be different line widths since the force line carries high current and the sense line doesn't. I also need these different line widths to flag errors when the DRC is run if not met.

    I have been doing a bit of research on this topic and have figured out how to accomplish a couple of these requirements. I found a link to an app note about using the NET_SHORT symbol to, from what I gather, merge nets at a physical padstack where all nets become electrically connected then finally connect to the DuT pin. This method is undesirable since it requires placing another component which takes room on a very dense board.

    I am currently using the SYNONYM part to connect the nets together in the schematic. This unforunately merges the nets in the Physical section of the Constraint Manager and forces one line width setting for the whole net. I tried to deal with this by using Pin Pairs in the net. I was able to separate the force line width from the sense line width. When I use the autorouter, it routes the lines correctly with the different line widths.

    This is great and almost what I need but it lacks any checks from the DRC if the line widths were to be changed or if it was routed by hand (my company routes most PCBs by hand due to the numerous critical traces).

    In the end, I am asking: how do I force the DRC to check minimum line width against the pin pair specs and not the net specs, if pin pairs exist?

    Thanks, Jack
    • Post Points: 20
  • Wed, Feb 2 2011 2:35 AM

    • steve
    • Top 10 Contributor
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    • Woking, Surrey
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    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

    You can do this but you need a PCB Editor Performance license to do it. Bascially schedule the net then using Constraint Manager create pin pairs of the net. Once this is done the pin pair groups are visible in Constraint Manager Physical Tab. You can assign a different PCSET to the different pin pairs.

    • Post Points: 35
  • Wed, Feb 2 2011 9:35 AM

    • jackg23
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    • Chandler, AZ
    • Posts 2
    • Points 40
    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

    I am using Allegro PCB Design XL 16.3S017 and I was able to schedule the nets, create the pin pairs of the net in the Physical tab, and assigned different PCSETs to each pin pair with my license. Do I still need the PCB Editor Performance license for it to perform a DRC on the physical constraints for pin pairs?

    Thanks,

    Jack

    • Post Points: 20
  • Wed, Feb 2 2011 11:10 AM

    • Brando
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    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

     I've had success with the DRC's correctly showing errors and using PCSets for Pin Pairs.  Make sure that after updating the Constraint Manager (CS) that you do a DRC udpate.

    I am having some problems with routing, though.  When routing traces (manually) between two pins of a pin pair, the line width always defaults to the NET line width, not the Pin Pair line width defined in the CS.  The line width in the options control box shows the correct width, but that is not what is drawn.  Then, I get a DRC that says the neck length is too long.  I'm assuming that this is because the tool does not know which pair of pins I'm connecting until after the trace is completed.  Does anyone know how to make the line width default to what is in the constraints manager?

    • Post Points: 20
  • Wed, Feb 2 2011 3:51 PM

    • Khurana
    • Top 25 Contributor
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    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

    >>When routing traces (manually) between two pins of a pin pair, the line width always defaults to the NET line width, not the Pin Pair line width defined in the CS

    Thereis was a bug - ensure that you've got the latest hotfix installed.

    • Post Points: 5
  • Thu, Feb 3 2011 8:15 AM

    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

    The pin-pair works nicely, but what if you dont have the luxury of having a pin to schedule. What if you need to connecto the sense line to the force line at a via or to the actual trace of the force line?

    • Post Points: 20
  • Thu, Feb 3 2011 10:44 AM

    • Brando
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    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

    I would create a pin pair for the force line and leave the sense line as default.  You can connect the sense line anywhere on the force line or to a via and the width would not be the same as the pin pair constraint width.

    • Post Points: 20
  • Fri, Feb 4 2011 10:06 AM

    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

    Thanks Brando. I tried creating a pin pair between the force resource line and the DUT pin, and not creating a pair for the sense pin (leaving it as default). When I grab the force pin to in route mode it default to the Min line width of the net, not the Min of the pin pair. What am I doing wrong? The line width in the router shows I want 30 (the value I asigned to the force pin pair) when I grab the pin it only shows the route at 6 (default value).

    • Post Points: 20
  • Fri, Feb 4 2011 10:30 AM

    • Brando
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    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

     That was actually my problem also.  See the above reply from KHurana.  I haven't installed the latest hotfix yet (waiting on the tools admin), but the release notes do address this issue.  In the mean time, if I see a line width in the options control box that is different than the default, I just type over that value and then the line width is correct.

    • Post Points: 20
  • Fri, Feb 4 2011 11:03 AM

    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

    I will check that there is a newest hotfix, but I do believe my compay has the latest releases. Do you know that date of the latest hotfis release? Thank you for all your help!

    • Post Points: 20
  • Fri, Feb 4 2011 11:19 AM

    • Brando
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    Re: Different Force and Sense Line Widths using Pin Pair Physical Constraints Reply

     It looks like it was fixed in hotfix 021 which was release 12-10-2010. 

    http://downloads.cadence.com/ESDWeb/ReleaseDetail.eo?methodToCall=viewReleaseDetail&platform=WINDOWS&releaseName=SPB163

    Look at item number 846352 of the README_CCR.txt:

    846352  ALLEGRO_EDITOR DRC_CONSTR       Route connect does not select the pin-pair width for routing.

     

    • Post Points: 5
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Started by jackg23 at 01 Feb 2011 03:48 PM. Topic has 10 replies.