Hi all,

I am verifying a design where parasitic path on layout may be critical. The layout has been extracted with Assura RCX in modality "only-R" and then back-annotate the parasitic on the Virtuoso schematic editor with "Parasitics" menu and "report terminal-to-terminal". Selecting the desired terminals I obtain a list of poly/metal resistance contributions and the sum of them all as expected.
But...
I repeated the Assura extraction with "RC" mode and repeated the back annotation between the same terminals and ... the result was different: the overall parasitic R on the same net was almost 50% higher!

I am puzzled because I thought that "only-R" extracted a subset of parasitics from "RC".

Did anybody of you find such behaviour?
I also tried to extract a parasitic spectre/spice netlist for visual inspection but I am not able to have the parasitics lumped (i.e. an RC pair for every net).

Any help is welcome.
Thanks in advance, bye.
Cristiano