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Calibre PEX extraction - capacitor value doubled after extraction

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Yakov_Yakov

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Hello.
I run Calibre PEX on simple circuit - only MOM capacitor of 40ff with 2 ports.
After extraction on test bench I got 88ff.
What is a problem and who I can fix it ?
Thank you in advance.

- - - Updated - - -

Probably the problem calls double-counting, but I can mistake...
 

erikl

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Calibre PEX extraction calculates and includes parasitics - that's exactly it's job.
 

Yakov_Yakov

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I check it only on capacitor without some additional and significant routing.
And probably , it takes into account both capacitance from cap model and extracted capacitance.
 

timof

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Hi Yakov -

this is actually a very common problem in extraction - called capacitance double-counting.
Your LVS recognizes MOM capacitor as a device, so it create a device instance for MOM capacitor, described by its SPICE model (probably a very simple one).
But, your extraction tool is not instructed to exclude MOM capacitor from capacitance extraction - extraction tool treats metal lines and vias of MOM capacitor as regular interconnects, and extracts their capacitance.
This exclusion of the device from extraction is called "device blocking".

You need to check or fix your extraction setup, to enable device blocking for MOM capacitor.

Max
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