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Simulators >> Circuit Simulators >> PSS simulation stopped by behavior device models.
https://designers-guide.org/forum/YaBB.pl?num=1322843111

Message started by Jacki on Dec 2^nd, 2011, 8:25am

Title: PSS simulation stopped by behavior device models.
Post by Jacki on Dec 2^nd, 2011, 8:25am

Hello,

I am facing a problem with PSS simulation. The thing is that I want to run swiched capacitor circuit with PSS and PAC. The simulation is find when I use ideal switch from Spectre. When I replace the ideal switch by the real transistors, there is an error shown below and stops the simulation.

ERROR (SPCRTRF-15177): The component nfeti_rf_ahdl is not supported in
PSS analysis because it is a behavior module component with hidden states.
Components with hidden state are not allowed with this analysis.The PSS
analysis is skipped.

I also try other models from the design kits, the same problem happens. I check the model in ADE, I think the spectre model has the highest priority for simulation as below
spectre ahdl veriloga

Does anybody face the same problem before? Is it the setting problem in Cadence, or I should contact the foundry and ask for help?

Thank you!

jacki

Title: Re: PSS simulation stopped by behavior device models.
Post by Geoffrey_Coram on Dec 5^th, 2011, 1:23pm

You should contact the foundry. "hidden state" is a problem for PSS; you can find many threads on this forum about it. But a well-written model will not have hidden state.

Title: Re: PSS simulation stopped by behavior device models.
Post by Jacki on Dec 6^th, 2011, 8:43am

Hello Geoffrey_Coram,

Thank you for your reply. I also check from cadence support. I try to change the engine from "shooting" to "harmonic balance", the same problem happens.

I think maybe it is because the foundry wants to keep some secrets for their design kits. I will contact the foundry.

Jacki

Title: Re: PSS simulation stopped by behavior device models.
Post by Frank Wiedmann on Dec 6^th, 2011, 9:19am

You are probably misinterpreting the meaning of "hidden state". Take a look at http://www.designers-guide.org/Analysis/hidden-state.pdf for an explanation of the problem.

Title: Re: PSS simulation stopped by behavior device models.
Post by Jacki on Dec 7^th, 2011, 10:02am

Hello Frank,

Thank you very much for your comments. Now my problem is I just pick up the device models from the foundry library, I don't think I can modify the models. I will try to find other ways to avoid it.

Actually I have no idea of the devices models. Usually we are talking about the device models based on BSIM model. What is the difference between spectre device model and verilog-A model? If spectre model is enough for the simulation, can I skip the verilog-A model, then the hidden state problem can be avoided.

Thanks.

Title: Re: PSS simulation stopped by behavior device models.
Post by Frank Wiedmann on Dec 7^th, 2011, 3:30pm

Verilog-A is a language that allows you to write models in the form of equations (see http://www.designers-guide.org/VerilogAMS/ for some examples). This makes it more flexible (but often also slower) than built-in device models like BSIM where the equations are part of the model and you only can specify parameter values.

As I have not seen your models, I have no idea what your foundry uses the Verilog-A for and if eleminating the Verilog-A part would still give you accurate simulation results (or what workarounds might be possible for your problem). You should probably discuss this question with your foundry (and refer them to Ken's paper as background information).

Title: Re: PSS simulation stopped by behavior device models.
Post by Jacki on Dec 8^th, 2011, 8:04am

Hello Frank,

Thank you for your comments.

Now the problem is solved. I think in the design kits, there are two kind libraries for Spectre. One library is ahdl models, and the other library should be based on BSIM models.

I change the library from ahdl to BSIM, then the PSS can run smoothly now.

thanks.

Title: Re: PSS simulation stopped by behavior device models.
Post by kollayliu on Jul 19^th, 2012, 2:06am

Hi Jacki,

Would you like to tell me more about how to switch from ahdl model to BSIM model?

Thanks

Title: Re: PSS simulation stopped by behavior device models.
Post by Geoffrey_Coram on Jul 19^th, 2012, 6:20am

You'll probably need to send a private message to Jacki if you want a response; this thread is very old.

That said, I would expect your foundry documentation to tell you how to set the library for simulation and what library options are available. Unless you're using the exact same process from the same foundry as Jacki, you'll need to look up the details for yourself.

Title: Re: PSS simulation stopped by behavior device models.
Post by kollayliu on Jul 19^th, 2012, 7:12am

Hi Geoffrey_Coram

Thanks. I already sent a message to Jacki. According to the name of model, i.e. nfti_rf_ahdl, it looks like we may use the technologies from the same foundry. Hopfully, he can see my message.

Title: Re: PSS simulation stopped by behavior device models.
Post by Geoffrey_Coram on Jul 19^th, 2012, 11:04am

Just a wild guess, but if you change the model to "nfti_rf" does that work?