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RobG

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Posts: 570
Bozeman, MT

Automatically calculating AD, AS, PD, PS, etc
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?

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Geoffrey_Coram

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Posts: 1999
Massachusetts, USA

Re: Automatically calculating AD, AS, PD, PS, etc
Reply #1 - 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?

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RobG Community Fellow Offline Posts: 570 Bozeman, MT	Re: Automatically calculating AD, AS, PD, PS, etc Reply #2 - 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!
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Geoffrey_Coram Senior Fellow Offline Posts: 1999 Massachusetts, USA	Re: Automatically calculating AD, AS, PD, PS, etc Reply #3 - 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.
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RobG Community Fellow Offline Posts: 570 Bozeman, MT	Re: Automatically calculating AD, AS, PD, PS, etc Reply #4 - 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.
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