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PVS LVS not flagging device W/L mismatches in gpdk045 (IC23.1 / PVS 23.11)

RK202509013321

Hello,

I am a teaching assistant for an IC design course, and I’m currently migrating our design flow to Cadence IC23.1 / PVS 23.11 with the gpdk045 PDK.

I have successfully run DRC and LVS. LVS reports as MATCH when connectivity and pins line up, but I noticed something strange:

  • If I deliberately change the device size (e.g., double the PMOS width in the schematic while keeping the layout the same), LVS still reports clean.

  • I expected LVS to flag a mismatch on the device width.

Environment details:

  • Virtuoso: IC23.1 (cadence/2024-08)

  • PVS: 23.11-s036

  • PDK: gpdk045_v_5_0

  • Rule deck: pvlLVS.rul

  • LVS run invoked from Virtuoso → Verify → PVS → LVS

What I tried so far:

  • Verified that LVS_CHECK_PROPERTY lines exist in the rule deck for MOS devices, e.g.:

    LVS_CHECK_PROPERTY MN ( g45n1svt ) l l -tolerance 0; LVS_CHECK_PROPERTY MN ( g45n1svt ) w w -tolerance 0;

  • Ensured I am generating the CDL netlist..

  • Tried both flattened and unflattened PCells.

  • Examined the comparison report (.cls file) — it shows devices matched, but parameters are not being compared.

Question:
Is there an additional option, switch, or rule deck directive I need to enable so that PVS LVS actually checks W/L mismatches?
Or does this require a specific setup in the PDK rule deck (e.g., mapping properties to schematic parameters)?

Any guidance on enabling strict property checking in PVS LVS would be greatly appreciated.

Parents
  • RobMan

    You might want to update the gpdk version (just for good measure). gpdk045_v_6_0 has been available for quite some time.

    My first port of call for the check would be the netlist.

     runName.cdl (schemaitic netlist)

     runName.spi (layout netlist)

    Check if the values are correct there before you address the comparison rules.

  • Andrew Beckett
    in reply to RobMan
    RobMan said:
    You might want to update the gpdk version (just for good measure). gpdk045_v_6_0 has been available for quite some time.

    I'd just checked using gpdk045_v_6_0 and then gpdk045_v_5_0 as Rob suggested; the problem shows up in the older PDK (with the same PVS version you're using). It works correctly with gpdk045_v_6_0. I believe this is because of a change in PVS some time ago, and the rule decks needed to be updated to add additional lvs_map_device rules to map the type from M to MP etc.

    Andrew

Reply
  • Andrew Beckett
    in reply to RobMan
    RobMan said:
    You might want to update the gpdk version (just for good measure). gpdk045_v_6_0 has been available for quite some time.

    I'd just checked using gpdk045_v_6_0 and then gpdk045_v_5_0 as Rob suggested; the problem shows up in the older PDK (with the same PVS version you're using). It works correctly with gpdk045_v_6_0. I believe this is because of a change in PVS some time ago, and the rule decks needed to be updated to add additional lvs_map_device rules to map the type from M to MP etc.

    Andrew

Children
  • RK202509013321
    in reply to Andrew Beckett

    Thanks Andrew and Rob. We do not have v_6. How can we get this version? Can you please let me know?

  • Andrew Beckett
    in reply to RK202509013321

    Go to http://pdk.cadence.com (this is a shortcut to a page on the support portal, and so you need a login to support.cadence.com (aka ask.cadence.com )). That's the location for downloading the generic PDKs.

    Regards,

    Andrew

  • RK202509013321
    in reply to Andrew Beckett

    Hi Andrew

    With the new GPDK045 v6, my LVS fails with “Missing power or ground” unless, during pin creation, I enable “Convert pin to geometry + text” instead of leaving it as “geometry” only. With previous PDK versions I did not need the text part for LVS to run cleanly. Do you know why this is the case or am I missing something? 

  • Andrew Beckett
    in reply to RK202509013321

    You'd normally need to either have the text on the pins (when you create the pin) or to use that option. I can't really see why this would be different between these two PDK versions, since nothing related to that changed...

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