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Simulators >> Circuit Simulators >> Illogical outputs in cadence (IC5141) ADE
https://designers-guide.org/forum/YaBB.pl?num=1329897833

Message started by VINAY RAO on Feb 22^nd, 2012, 12:03am

Title: Illogical outputs in cadence (IC5141) ADE
Post by VINAY RAO on Feb 22^nd, 2012, 12:03am

Hello all,
I installed cadence in a fresh drive which included base of IC5141 and hotfix of IC5141 in a separate folders. As a supporting package, I have installed updates of MMSIM 10.1 and IUS 8.2 (& many other like Assura, pacific etc). For checking the installation, simple inverter is drawn in schematic editor and voltage sources are taken from AnalogLIB. After setting up the schematic, I tried to simulate it in ADE (using UMC90nm foundry) by choosing the spectre simulator. It couldn’t simulate and threw the following error (This error appeared only if I am running workstation from hotfix but not with the base).
“*ERROR* Errors encountered during simulation. The simulator run log has not been generated. Possible cause could be an invalid command line option for the version of the simulator you are running. Choose setup-> Environment and verify that the command line options specified in the userCmdLineoption field are supported for the simulator. Alternatively, run the simulator standalone using the runsmulation file in the netlist directory to know the exact cause of the error.”
This is not a serious problem and found the solution through googling. Solution was to empty the maxnotes & maxwarns field which is found in simulator options (ADE->Simulation->option->analog->simulator options). After doing this, simulation ran successfully but got an illogical output. This is the serious illogical result which I am not able to resolve it. Details are given below.
First I tried with DC analysis (source voltage varied from 0 to 1v) and tried to plot DC response from both source voltage and as well as from the output of the inverter. I attached those results with this query. DC response (first row in result) from THE SOURCE IS NOT A LINEAR CURVE AS EXPECTED rather response is of some kind of noise (though I didn’t select any kind of noise options). One thing to observe is that, voltage coming in Nano volts. Output response is fine but it is sweeping from 1 to -1 as against the expected 1 to 0.
Secondly I tried with pulse voltage source from again analogLib but got into trouble again. Here again output response is fine but plotted source voltage is coming in terms of micro volts.
Can anyone explain, how can I resolve it? Is it because of simulator/mmsim/analogLib/maxnotes settings?
Your help would be highly appreciated. Thank you.

Title: Re: Illogical outputs in cadence (IC5141) ADE
Post by VINAY RAO on Feb 22^nd, 2012, 9:34pm

Solved
VINAY RAO wrote on Feb 22^nd, 2012, 12:03am:

First of all, thanks to Andrew Beckett for his valuable suggestions.

About first problem:In my script file, path for <IC5141instDir>/tools/bin and <IC5141instDir>/tools/dfII/bin was mentioned above the <MMSIMinstDir>/tools/bin. So I changed it and now it works fine with the default maxnote and maxwarn values.

About second prob:I couldn’t sort out this problem (might be the connection problem but couldn’t find) and hence I created a new cell view and I drew the same circuit again. With the new cell view, I am getting the exact output what one can expect.

Regards,
Vinay Rao.

Title: Re: Illogical outputs in cadence (IC5141) ADE
Post by Geoffrey_Coram on Feb 23^rd, 2012, 8:29am

VINAY RAO wrote on Feb 22^nd, 2012, 12:03am:

... response is of some kind of noise (though I didn’t select any kind of noise options).

It's numerical (round-off) noise. nV are below the default tolerance (vntol), so the simulator is really giving you zero. I agree it's probably a connection problem. (It could be something like the fact that Spectre is case-sensitive, so VDD and vdd are different nets.)