RE: [IBIS-Users] Ccomp extraction via Tank method

Hi, Lars,

There have been several papers on C_comp extraction at the IBIS summits.
They note that C_comp depends on both bias voltage and frequency, so it is
impossible to extract a "single" value using this method.

The preferred approach is to make a linear fit to a ramp voltage response
(ramp voltage at full-logic-swing; I=C*dv/dt=constant=linear fit).  This is
close to what the I/O will see in an actual PCB.

Best regards,
Lynne


"IBIS training when you need it, where you need it."

Dr. Lynne Green
Green Streak Programs
http://www.greenstreakprograms.com
425-788-0412
lgreen22@mindspring.com


-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of Lance Wang
Sent: Thursday, March 12, 2009 12:52 PM
To: 'Lars Snith'
Cc: ibis-users@eda.org
Subject: RE: [IBIS-Users] Ccomp extraction via Tank method

Hi, Lars,

I would suggest you to try a larger swing for Vdc. Sometimes, in certain Vdc
range, c_comp may not change significantly. 

Also, you can post your test case and results to the reflector or send to
me. I am interested to find out.

Regards,

Lance Wang
978-764-2298
IO Methodology Inc.


-----Original Message-----
From: owner-ibis-users@server.eda.org
[mailto:owner-ibis-users@server.eda.org] On Behalf Of Lars Snith
Sent: Thursday, March 12, 2009 1:15 PM
To: Lance Wang
Cc: ibis-users@server.eda.org
Subject: Re: [IBIS-Users] Ccomp extraction via Tank method

Hello Lance,

Yes, by varying the DC component of the AC source in alter statements:
Vsw Sweep2 gnd dcoffset AC

Best regards,  Lars

Lance Wang wrote:
> Hi, Lars,
> Did you change Vdc value?
> 
> Lance Wang
> 978-764-2298
> IO Methodology Inc.
> 
> 
> -----Original Message-----
> From: owner-ibis-users@server.eda.org
> [mailto:owner-ibis-users@server.eda.org] On Behalf Of Lars Snith
> Sent: Thursday, March 12, 2009 11:29 AM
> To: ibis-users@server.eda.org
> Subject: [IBIS-Users] Ccomp extraction via Tank method
> 
> Hello All,
> 
> For Ccomp extraction I have so far relied on Time Domain methods. But 
> as shown in the documentation (link below) the result is not always
> reliable.   http://www.eda.org/ibis/summits/jun02/hegazy.pdf
> 
> I have put together a simple testbench to play around with the Tank 
> method, and true enough values are not especially sensible to any of 
> supply, temperature or even process variations.
> 
> However, before I embark on wrapping up a new flow for myself I 
> thought I'd just ask this forum if there is already a recommended 
> testbench for the Tank method out there? If so, I'd be most interested to
share.
> 
> 
> Best regards,  Lars

--
Those who can, Do
Those who can't, Simulate

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