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Modeling >> Passive Devices >> Resistance value mismatch (LVS mismatch)
https://designers-guide.org/forum/YaBB.pl?num=1205293371

Message started by santosh_iitkgp on Mar 11^th, 2008, 8:42pm

Title: Resistance value mismatch (LVS mismatch)
Post by santosh_iitkgp on Mar 11^th, 2008, 8:42pm

Hi,

I have designed a circuit using IHP technology (SG25H1M4) in cadence. In this circuit, I have used a rppd resister with a value of 260.143 Ohm, both in schematic and layout. Now, whenever I am running the LVS, it shows a different value (14548 Ohm) for rppd resistor used in layout.

Would you please tell me, why this is happening and how can it be solved.

Thanks,
Santosh.

Title: Re: Resistance value mismatch (LVS mismatch)
Post by Geoffrey_Coram on Mar 12^th, 2008, 11:58am

Did you check the layout, to make sure the length and width were what you expected? (Measure them.) You should then be able to estimate the resistance from the sheet rho in the model file.

Could be the LVS runset has a bug in the resistance calculation. Put down a couple rppd devices with different numbers of squares and see if you get a consistent sheet rho -- and then try a couple different geometries with the same number of squares (L/W, 2L/2W, etc.). You might get slightly different answers because you'll get more contacts with a double-wide device.