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 sweeping w/L ratio 

Last post Wed, Jul 22 2009 4:54 AM by tkhan. 4 replies.
Started by whlinfei 22 Jul 2009 01:04 AM. Topic has 4 replies and 1934 views
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  • Wed, Jul 22 2009 1:04 AM

    • whlinfei
    • Top 500 Contributor
    • Joined on Sun, Mar 15 2009
    • Posts 24
    • Points 435
    sweeping w/L ratio Reply

    Hi all,

     I am new to cadence and I tried to sweep a mosfet w/L ratio under a dc sweep. ( for every w/l , a gate bias dc analysis is run from 0 to Vdd).

    However I tried to define my variable as "param" to indicate the number of fingers so that I could change the total width but couldt get the result.

     Can anyone help me with this ? 

    I am using vurtuoso schematic to design and vurtuoso analog design environment to simumlate. 

    • Post Points: 20
  • Wed, Jul 22 2009 1:09 AM

    Re: sweeping w/L ratio Reply

    This may depend on your design kit. Some design kits over-use CDF callbacks, which prevent you being able to parameterize certain parameters. See The Dangers of CDF Callbacks (written by me) on sourcelink.

    Regards,

    Andrew.

    • Post Points: 20
  • Wed, Jul 22 2009 1:17 AM

    • whlinfei
    • Top 500 Contributor
    • Joined on Sun, Mar 15 2009
    • Posts 24
    • Points 435
    Re: sweeping w/L ratio Reply

    hi

    thanks for your reply.

    However I couldn't view your documents as I don't have access to sourcelink. ( couldn't register)

    Can you send me a copy of that ?

    for my design, I just put parameter in the number of fingers box when editting the instance property. Not sure if it's allowed. 

    And I am using ibm 130nm CMSF8SF. I don't know how to use the callback you mentioned. Can you kindly tell me ?

    thanks .

     

    Best Regards,

    whlinfei 

    • Post Points: 35
  • Wed, Jul 22 2009 1:28 AM

    Re: sweeping w/L ratio Reply

    To be honest, the solution is not going to help you very much anyway, because it's more about describing how to create a PDK which doesn't use callbacks, or uses them in such a way to not have this problem.

    I don't have access to the PDK you're using, so I can't offer that  much advice. When you enter a parameter name in the parameter field, do you get any errors in the CIW? CDF callbacks are defined in the CDF for each field for the component in question (you should be able to see them in Tools->CDF->Edit CDF and pick the component you're using), and are often used to derive one parameter from another. So for example, if you enter width and or fingers, and it auto-calculates total width, then that is done by a CDF callback. The question is often which parameters actually get netlisted - this is controlled by the simulation information section.

    The PDK User Guide (assuming there is one) may describe what is and isn't supported, so it's worth reading that. Essentially you can probably figure it out by entering parameters in various fields, checking for errors in the  CIW, and seeing what gets netlisted.

    Regards,

    Andrew.

    • Post Points: 5
  • Wed, Jul 22 2009 4:54 AM

    • tkhan
    • Top 50 Contributor
    • Joined on Sat, Aug 16 2008
    • Toronto, Ontario
    • Posts 159
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    Re: sweeping w/L ratio Reply

     Are you sweeping number of fingers (i.e. Width of single finger) for a fixed W (i.e. Width of all fingers)? I don't think you can do that in IBM8RF unless you edit the CDF parameters as Andrew mentioned. There are many parameters in the model defined by "Width of all fingers" and "Length" in the instance properties. If you're with MOSIS ask them if theres a way to do this. support@mosis.com or http://tech.groups.yahoo.com/group/MOSIS_Users_Group/. Also in the CDSLIB users guide there is a section on CDF parameters, you might want to take a look at that.

    • Post Points: 5
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Started by whlinfei at 22 Jul 2009 01:04 AM. Topic has 4 replies.