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Simulators >> Circuit Simulators >> Automatically calculating AD, AS, PD, PS, etc
https://designers-guide.org/forum/YaBB.pl?num=1205206548

Message started by RobG on Mar 10^th, 2008, 8:35pm

Title: Automatically calculating AD, AS, PD, PS, etc
Post by RobG on Mar 10^th, 2008, 8:35pm

I know this can be done easily, but I can't seem to get to first base.

When I place a mosfet using the cadence schematic capture tool, and give it a certain width, I would like the AD, AS, parameters automatically filled out (even if I have to use simplified formulas). I know there must be a file somewhere where you define these based on the width. Can someone direct me to this file or give me a hint one what I should be searching for in the help?

Title: Re: Automatically calculating AD, AS, PD, PS, etc
Post by Geoffrey_Coram on Mar 11^th, 2008, 8:35am

To compute the value, you need to know the diffusion dimension perpendicular to the width (note: it's not the gate length).

Are you asking how to get that value? Or are you asking how you set up the Cadence CDF (component ... form) with a callback so it fills in the values automatically? (Change the width, callback changes AD and AS.) Or are you wanting to change your netlister to print out a default AD=value if there's no value specified in the form?

Title: Re: Automatically calculating AD, AS, PD, PS, etc
Post by RobG on Mar 11^th, 2008, 9:15am

I know the formulas and diffusion dimensions; I just need to set up the CDF that will fill the values automatically, e.g. AD=w*0.4u. Right now I'm filling out the form by hand. Your help would be enormously appreciated!

Title: Re: Automatically calculating AD, AS, PD, PS, etc
Post by Geoffrey_Coram on Mar 11^th, 2008, 10:19am

You'll have to search the directory tree for your PDK -- though perhaps CDS.log will give you some hints. You're looking for files ending in .cdf, they're written in skill.

Title: Re: Automatically calculating AD, AS, PD, PS, etc
Post by RobG on Mar 11^th, 2008, 3:44pm

Thanks for the hints - they help a lot.

Another person pointed out that it can be done with iPar("w") in the CDF. This is much easier.