PSPICE-FOR-TI: Resistor Tolerance < 1%

Hi Drew,

Can you confirm that you used the '%'?  Did you enter 0.26%, or just 0.26?

I'll also check with Cadence. I didn't see anything in the manual regarding a limitation on the size/precision of the tolerance.

David

Hi David,

Yes, I have the parameters defined like this. I've tried 0.26% and .26% and they both vary R_top and R_bot by 26% while R_LOAD varies by the proper amount.

Thanks,

Drew

Thanks for the confirmation. I've submitted a question on this to Cadence. All the examples that I've seen have 10%, or 5%. I asked if this is an integer field, and where it is specified in their manual.

David

Appreciate it David!

Hi David,

I just discovered this happening on the other tolerance that is >1%. I was running a worst-case analysis for Vout with:

• device tolerances only
• limited to type R.
• greatest difference from the nominal run
• worst case direction high

In this case, RLOAD was the only resistor with a tolerance for this sim. Across the 3 runs it did, RLOAD varied positively by 1% and negatively by 165% so it ran at -1.43ohms. This is even more egregious than the previous case since it's making the resistance negative. Just wanted to let you know in case it helps the investigation.

-Drew

Thanks. Waiting on word from Cadence about this.I don't expect to hear anything today. 

What run number are you using for your monte carlo? 500, 1000?

Hi David,

I've only run the worst case analysis, with the regulator output voltage as the output variable. When I get to Monte Carlo I'd probably start with 200 and go from there.

-Drew

Hi Drew,

Can you send over the project and associated files? Thankfully, there won't be any .dat file to blow up the file size.

Cadence was unable to replicate on their end, so would like to try on your specific test bench.

David

Hi David,

Please see the attached project archive.

Best,

Drew

TOL_TEST.zip

Hi Drew,

I've passed this on. Haven't heard back yet.

David

I've downloaded and am running a sim. Files in download only included design1.opj, cmc_max4210.dsn, and design1-PSpiceFiles.. When I opened the proj, it created a new folder, CMC_MAX4210-PSpiceFiles. No libraries though.

I assume the OPAMP is ideal, and that the TPS62130A is standard from TI. My local copy must be pulling from the built in library.

Can you archive again and include libraries? I want to make sure that we're working with the same setup.

David

Hi David,

Yes, the op amp is ideal and the TPS62130A was an included library. I changed up my designs a bit and removed the tolerances. When I work out some other details I'll send over the new project with the libraries included. I won't be using anything that isn't part of the default libraries.

-Drew

Hi David,

I didn't realize how close I was to finishing up the design so here is the latest with the libraries. Please let me know if this one imports correctly. I just ran a WC analysis and the issue persists.

Best,
Drew

TOL_TEST_v1_TI.zip

Thanks. I've passed this on to Cadence. They weren't able to simulate the original TOL_TEST while I was able to. Not sure why.

Hopefully, this zip with libraries will allow them to simulate and identify the issue.

David

Appreciate the help! Fingers crossed.

Hi David,

Thanks for the update! That's interesting behavior, but I'm glad you were able to find a workaround for it. I will remove the tolerances from the parameter list.

-Drew