[SI-LIST] Re: Ground bounce
- From: "Raymond Y. Chen" <chen@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Fri, 16 Jul 2004 12:30:06 -0700
R.K and Jim,
Defining ground bounce as a voltage across so-called a "ground inductance",
such as the case in the app note mentioned below, is misleading and not
appropriate.
We see very often ground bounce is defined by the following diagram,
-------PAD
|
|
NMOS
|
|<<internal GND
INDUCTOR
|
GROUND PIN
which is based on an assumed circuit model. However since this circuit model
itself is flawed, we better re-exam "ground bounce" as a physics term
"voltage" that is related to the real-world physical structures.
#1 what does this "ground inductor" represent? power ground loop, or signal
ground loop? Is it meaningful to define the inductance of a single conductor
without considering the return path (loop)? If it is a partial inductance,
then where is the mutual inductance that has to be present?
#2 is measuring voltage between chip internal GND vs. PCB GND meaningful at
high frequency? Do we have a probe that allows us to measure voltage across
large distance in the lab?
The answers to these questions are embedded in some good technical
discussions in SI-List. I would suggest to read the following two postings:
[SI-LIST] Re: SSO pushout, ground bounce definition
(//www.freelists.org/archives/si-list/04-2002/msg00107.html)
[SI-LIST] Re: SSO pushout, ground bounce definition
(//www.freelists.org/archives/si-list/04-2002/msg00115.html)
And other related posts for that thread are also very helpful to clarify
some of the myth associated with ground bounce, ground inductance, partial
inductance, etc.
regards,
Raymond Y. Chen
Sigrity, Inc.
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Jim Antonellis
> Sent: Thursday, July 15, 2004 9:24 PM
> To: rkreddy@xxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Ground bounce
>
> R.K.
>
> Although I could explain it, a quick Google search provides a
> wealth of material on it like the one below (with pictures!).=20
> I am not advocating nor approving this particular app note,=20
> but it looks about right to get you going:
>
> http://www.fairchildsemi.com/an/AN/AN-640.pdf
>
> Furthermore, if you're asking this level question,
> may I recommend a book like Johnson and Graham'
> "High Speed Digital Design", as one of the many=20
> excellent texts on signal integrity.
>
> Jim
>
>
> -
> Jim Antonellis jim.antonellis@xxxxxxxxxxxxx
> Sandburst Corp www.sandburst.com
> Office: 978.689.1669=20
> Cell: 978.618.4745
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Ramkrishna Reddy
> Sent: Sunday, July 15, 2001 11:53 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Ground bounce
>
> Hi,
> Can anybody explain me what is ground bounce and how to overcome the =
> ground bounce problem.
> Thanks
> R K Reddy
> ------------------------------------------------------------------
>
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