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Parasitic Report-NS/NA values

Monady

Hi,

We are using IC6.1.6-64b 64-bit, MMSIM 13.1
I tried using parasitic report for the extracted view of my circuit. I followed all the guidelines and read the parssim document. Then I run DC simulation and was looking for the R parasitics.

When I look at the schematic, some nodes have the reported R, and some have only NS and NA. I looked at CIW and it shows this message:

"*WARNING* (PARA-704) Effective R calculation has ignored the current and power from one or more parasitic resistors on net /I1940/Q1_H, as the resistor current was too low. Such currents are numerical noise from the simulator convergence algorithm and can consequently generate unreliable values. Decrease the simulator options "iabstol" and "vabstol" to reduce noise and provide a more accurate current through the resistor. If the currents are known to be accurate, you can modify the environment setting "mspsAv.currentThresholdScale" to change the multiplication factor applied to "iabstol" when checking for low currents."

I tried decreasing "iabstol" and "vabstol" values to the extent for some values it takes 3 hours to perform DC simulation, and for some "iabstol" and "vabstol" values the simulator does not converge anymore. I wonder is there any way to get parasitic resistance for all nodes. By the way, I didn't know how to change the environment setting "mspsAv.currentThresholdScale", and I am not sure if that would help or not.

Ps.: I just noticed I didn't post my question in the right section, but I cannot move it anymore :(

Any help will be appreciated.

Parents

  • Hi Monady

    Thanks for making an effort to state the version of Virtuoso and Spectre. Just a little info for you, it would be best to provide the full version number by executing "virtuoso -W" cmd in a terminal window. This is because "IC6.1.6-64b" only tells us that the version is "IC616" and you are using 64bits. But it does not let us know the sub-version (e.g. IC616-500-1 or IC616-500-6 or IC616-500-14, etc). Knowing the sub-version is very important in providing the correct debugging info.

    You can check the variables by entering the following cmds in CIW:

    envSetVal("mspsAv" "currentThreshold" 'float 1e-12)
    envSetVal("mspsAv" "currentThresholdScale" 'float 5)

    Please change 1e-12 and 5 to suitable values.


    Best regards
    Quek


    IC6.1.6-64b#sthash.WHNBT2NP.dpuf

Reply

  • Hi Monady

    Thanks for making an effort to state the version of Virtuoso and Spectre. Just a little info for you, it would be best to provide the full version number by executing "virtuoso -W" cmd in a terminal window. This is because "IC6.1.6-64b" only tells us that the version is "IC616" and you are using 64bits. But it does not let us know the sub-version (e.g. IC616-500-1 or IC616-500-6 or IC616-500-14, etc). Knowing the sub-version is very important in providing the correct debugging info.

    You can check the variables by entering the following cmds in CIW:

    envSetVal("mspsAv" "currentThreshold" 'float 1e-12)
    envSetVal("mspsAv" "currentThresholdScale" 'float 5)

    Please change 1e-12 and 5 to suitable values.


    Best regards
    Quek


    IC6.1.6-64b#sthash.WHNBT2NP.dpuf

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