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Design >> Analog Design >> Mismatch coefficient of Capacitors for gpdk 180nm technology
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Message started by indra0804 on Oct 29^th, 2013, 11:24pm

Title: Mismatch coefficient of Capacitors for gpdk 180nm technology
Post by indra0804 on Oct 29^th, 2013, 11:24pm

Hi experts,

I am designing a 8 bit CDAC for the SAR ADC that I want to design for my masters project. Regarding this, I want to know about mismatch coefficient of capacitors (Ac) for gpdk 180 nm tech. because, using the mismatch concept I can decide on the LSB cap value that I need to use.

Anyone having any information regarding this, please help me out....

Regards,
Indrajit

Title: Re: Mismatch coefficient of Capacitors for gpdk 180nm technology
Post by aaron_do on Oct 30^th, 2013, 2:50am

Hi,

It might be in the PDK docs, or if you have mismatch models, you could run a monte carlo analysis.

Aaron

Title: Re: Mismatch coefficient of Capacitors for gpdk 180nm technology
Post by indra0804 on Oct 30^th, 2013, 4:18am

Aaron,

I have checked the GPDK documentations available, but could not find anything mentioned over there. Also, about the monte carlo simulation that you are talking, can you elaborate a little bit more, like what kind of model to use for finding capacitor mismatch...

Anywayz, thanks for the reply.

Regards,

Indrajit

Title: Re: Mismatch coefficient of Capacitors for gpdk 180nm technology
Post by tm123 on Oct 30^th, 2013, 10:19am

There should be a mismatch model file included as part of the PDK. It is usually called something like mismatch.scs or montecarlo.scs. That model file should include the mismatch data for different devices. It could also be a section of the typical model file. Just open the model file you are using to see what is included.

Title: Re: Mismatch coefficient of Capacitors for gpdk 180nm technology
Post by ywguo on Oct 31^st, 2013, 8:11pm

Hi indra0804,

GPDK is a generic PDK, which has nothing to do with any real foundry process. I don't think it has mismatch data for Monte Carlo simulation.

Go to ask for the PDK from your foundry.

Best Regards,
Yawei

Title: Re: Mismatch coefficient of Capacitors for gpdk 180nm technology
Post by harpoon on Nov 1^st, 2013, 3:02am

Hi indrajit,

I happen to have Cadence's GPDK 180 installed (mainly for play).

If you look at the model files, you will find a file called

capacitor.scs

In this model file, you will find some statistics being applied to the cap model (under the "statistics" heading).

Looking at how the model file is written, the statistics part of the model is always included in the netlist ... then it is up to the simulator whether to use it or not.

So in short, if you just need to run ADE XL and set the run mode to Monte Carlo sampling. I think the Cadence docs will be able to help further.

Having said all that ... be warned that this GPDK is NOT a proper foundry PDK ... no clue whether the cap mismatch is realistic or not !

As Yawei mentioned, you are better off designing with a real PDK.