Designer’s Guide Community

Jacki

Senior Member

Offline

Posts: 237

PSS simulation stopped by behavior device models.
Dec 02^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

Back to top

IP Logged

Geoffrey_Coram Senior Fellow Offline Posts: 1999 Massachusetts, USA	Re: PSS simulation stopped by behavior device models. Reply #1 - 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.
Back to top	If at first you do succeed, STOP, raise your standards, and stop wasting your time. IP Logged

Jacki Senior Member Offline Posts: 237	Re: PSS simulation stopped by behavior device models. Reply #2 - 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
Back to top	IP Logged

Frank Wiedmann Community Fellow Offline Posts: 678 Munich, Germany	Re: PSS simulation stopped by behavior device models. Reply #3 - 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.
Back to top	IP Logged

Jacki

Senior Member

Offline

Posts: 237

Re: PSS simulation stopped by behavior device models.
Reply #4 - 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.

Back to top

IP Logged

Frank Wiedmann

Community Fellow

Offline

Posts: 678
Munich, Germany

Re: PSS simulation stopped by behavior device models.
Reply #5 - 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).

Back to top

IP Logged

Jacki

Senior Member

Offline

Posts: 237

Re: PSS simulation stopped by behavior device models.
Reply #6 - 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.

Back to top

IP Logged

kollayliu Junior Member Offline Posts: 22	Re: PSS simulation stopped by behavior device models. Reply #7 - 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
Back to top	IP Logged

Geoffrey_Coram

Senior Fellow

Offline

Posts: 1999
Massachusetts, USA

Re: PSS simulation stopped by behavior device models.
Reply #8 - 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.

Back to top

If at first you do succeed, STOP, raise your standards, and stop wasting your time.

IP Logged

kollayliu Junior Member Offline Posts: 22	Re: PSS simulation stopped by behavior device models. Reply #9 - 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.
Back to top	IP Logged

Geoffrey_Coram Senior Fellow Offline Posts: 1999 Massachusetts, USA	Re: PSS simulation stopped by behavior device models. Reply #10 - Jul 19^th, 2012, 11:04am Just a wild guess, but if you change the model to "nfti_rf" does that work?
Back to top	If at first you do succeed, STOP, raise your standards, and stop wasting your time. IP Logged