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PVS QRC / Calibre PEX both extracting 3x lower Resistance (Read 251 times)
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PVS QRC / Calibre PEX both extracting 3x lower Resistance
Dec 30th, 2016, 7:25am
Hello all,

I am trying to extract one half of an IC using CALIBRE PEX. We are most interested in R on our PWR/GND Rails. We have a really wide ground rail running horizontally (around 40 squares. So knowing this we expected a certain R to be calculated. But on probing using Calibre probes the resistance is calculated as roughly being 3x lower.

At this point I tried a few different things:
1) Tried a simple test case with the same metal layer and the tool seems to extract correct R when probed
2) Took the same exact layout, kept only the metal layers (and deleted all other layers) and did extraction with the same settings as before and got the correct R Value!
3) Also tried QRC with PVS, where the R being extracted is also incorrect.

If anyone has any other ideas or inputs then please let me know..  There is parallel metal to this thick ground layer of 40squares but in thicker layers and based on experiment 2) above this is not the issue.
I know these tools do not extract substrate resistances, so I am at a loss as to what could be going on. Also the design has 8 instances of the same subcell tapping off this ground rails fairly evenly all the way across. I have also checked if there are multiple pins or labels floating around on the GND rails, and that is not the case. Could it be that the tool does not care as to how accurate the R is if it is lets say less than an ohm..
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