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[Assura QRC] In what conditions can inductance be extracted?

bjbit

I am testing if I can extract inductance parameters from any layout using Assura QRC "RLCK". However, in the extracted SPICE file, there is no inductance records, while resistance and capacitance extractions are working properly. Here I attach the images of a simple inverter layout and its QRC setting. Anything I am missing? Thanks in advance.

   

  • Hi bjbjt

    It should be that parasitic inductors have already been extracted but were filtered due to large filtering size. Would you please check the filter size in "Filtering" tab of the QRC form? You can also check QRC log file for more details. There should be some messages if inductors have been filtered.


    Best regards
    Quek

  • Hi Quek,

    Thanks for advices. I have read the filtering section in user guide, and it seems only the option of "filter size" relates to inductance extraction. Then I redrew the wires with larger size (around 1 micron), and set "filter size" to min value 0.25 micron. However, the extraction still reports no inductance. Here are images of the new layout, and SPICE output. Any further advices? Thanks again.
     
    Regards,
    bjbit
     
     
     
     

  • Hi bjbjt

    Would you please upload your qrc.log file as an attachment (Please do not cut and paste into the reply)?

    Thanks
    Quek

  • Hi bjbjt

    You are running return-limited inductance extraction using QRC 11.1.0-p337. I see the following warnings in the log file:

    WARNING (ADVGN-221293): No inductances were extracted from the design 
    even though inductance extraction was run.
WARNING (ADVGN-221294): Check the ?rcxplNetFile and ?userRegion files for errors 
    that may have prevented inductances from being extracted.

    Would you please enable the PEEC buttion, select the entire cellview as the region and retry? It could be that return-limited is unable to find suitable inductors if your layout is too small.


    Best regards
    Quek

  • Hi Quek,

    I have tested and found that both PEEC and return-limited extractions work fine with user defined region. I will need to figure out why automatic partition for return-limited method fails to find inductor shape. Anyway, thanks again for your time and helps.

    Sincerely,

    bjbit 

  • Hi bjbjt

    Thanks for the follow-up. In that case, perhaps it might be good to file a service request to your local Cadence support with your testcase. QRC behaviour looks a little strange.


    Best regards
    Quek

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