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Design Languages >> Verilog-AMS >> Verilog-A speed in Spectre
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Message started by omar on May 21^st, 2010, 11:27am

Title: Verilog-A speed in Spectre
Post by omar on May 21^st, 2010, 11:27am

Hi,

I implemented a compact model of a transistor as a Verilog-A block in Spectre. I then simulated two identical circuits in Spectre. One circuit used the BSIM model for the transistors, which is built into Spectre, and the other used the compact Verilog-A blocks for the transistors. The circuit with the Verilog-A blocks as transistors was about 2x slower than the BSIM circuit. What is the reason for this speed difference? I think that the compact transistor model I implemented is much simpler than the BSIM. Is there any way to make the Verilog-A circuit run faster?

Thanks

Title: Re: Verilog-A speed in Spectre
Post by Geoffrey_Coram on May 24^th, 2010, 8:07am

What version of Spectre are you running? Can you get the latest?

How well coded is your Verilog-A model? Have you been sure to make your currents and charges continuous in a few derivatives?

Compare the information from the simulator on the number of timepoints in the two cases. I don't recall if Spectre gives you the number of iterations, but ideally you could compare both and make sure that your VA model isn't taking too many timepoints or too many iterations, either of which indicates a poorly-written model.

Title: Re: Verilog-A speed in Spectre
Post by omar on May 25^th, 2010, 3:06pm

I should be able to get the latest version of Spectre. I'm not sure how well written the code is. I believe all derivatives are continuous. Are there any resources which help with writing the code better?

Title: Re: Verilog-A speed in Spectre
Post by Geoffrey_Coram on May 26^th, 2010, 4:45am

I'm glad you asked! :)

http://www.bmas-conf.org/2004/presentations/bmas04-coram-preso.pdf

Title: Re: Verilog-A speed in Spectre
Post by Yuval on Jun 22^nd, 2010, 7:28am

omar wrote on May 25^th, 2010, 3:06pm:

Omar,

I recently started working on a verilogA Bsim3v3 model (I'm still in early stages since verilogA is new to me), can you share your model? I'll try to work on it with you and hopefully help improve it.
I have access to all Cadence tools and latest Spectre version (amongst other tools).

BTW, Geoffrey article is great place to start... Thanks

Best regards,

Title: Re: Verilog-A speed in Spectre
Post by Geoffrey_Coram on Jun 22^nd, 2010, 8:36am

Silvaco has a BSIM3v3 Verilog-A code available on their downloads site. I think you still have to create a login, but they recently updated their license agreement for Verilog-A models to differentiate these models from their own proprietary software. You might want to check what they've got and see if it suits your purpose.

Title: Re: Verilog-A speed in Spectre
Post by Geoffrey_Coram on Sep 2^nd, 2014, 2:43pm

Note: it appears that the web site www.bmas-conf.org is no longer that for the Behavioral Modeling and Simulation workshops.

Title: Re: Verilog-A speed in Spectre
Post by Ken Kundert on Sep 6^th, 2014, 11:49pm

The BMAS archives have been moved here.

-Ken