[SI-LIST] Re: AC series capacitor position in high speeddifferential signals
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Istvan Novak" <istvan.novak@xxxxxxx>
- Date: Thu, 13 May 2010 09:27:50 -0700
I would maintain from my measurements that the reflections are negligibly
small.
I would also maintain that simulation results, no matter what the tool or
operator, should not be trusted until they are validated by measurements to
insure the modelling is accurate. I've seen too many simulations done
incorrectly which were used to develop design rules that were either
ineffective or caused problems that I, for one, will not use the results of
unvalidated simulations.
Each engineer can make up his or her own mind on this, but my experience
says validate simulation results before betting any money on them.
I'm not trying to offend anyone who does simulations, just advising proceed
with caution.
Lee
> [Original Message]
> From: Istvan Novak <istvan.novak@xxxxxxx>
> To: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
> Cc: fei xue <harrison_cls@xxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> Date: 5/12/2010 8:55:32 PM
> Subject: Re: [SI-LIST] Re: AC series capacitor position in high
speeddifferential signals
>
> Lee,
>
> As it was pointed out in earlier threads, location does make a
> difference unless reflections are
> negligibly small. Assuming linearity, when we move components around,
> reciprocity prevails,
> but voltage transfer function from source to load will change, which in
> turn impacts eye
> parameters.
>
> Regards,
>
> Istvan Novak
> Oracle-America
>
>
> Lee Ritchey wrote:
> > This has been answered before on this forum. Since the circuits are
> > linear, it does not matter from a signal integrity point of view.
> >
> > Lee
> >
> >
> >
> >> [Original Message]
> >> From: fei xue <harrison_cls@xxxxxxxxxxxx>
> >> To: <si-list@xxxxxxxxxxxxx>
> >> Date: 5/12/2010 11:35:49 AM
> >> Subject: [SI-LIST] AC series capacitor position in high speed
> >>
> > differential signals
> >
> >> Hello all,
> >> We often can get different guideline of placing capacitor position when
> >>
> > placing AC series capacitor on high speed differential signals, like
PCIe,
> > SAS or LVDS signals. sometimes we followed the guideline to put
capacitors
> > near driver, sometimes near multi-connection connectors or sometimes
put it
> > near receivers.
> >
> >> Could anybody tell me what is the consideration of capacitor placing
> >>
> > position? Thanks!
> >
> >> Harrison
> >>
> >>
> >>
> >>
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