[SI-LIST] Re: AC series capacitor position in high speeddifferential signals
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Thu, 13 May 2010 10:24:41 -0700
I don't trust either if they don't agree.
> [Original Message]
> From: Muranyi, Arpad <Arpad_Muranyi@xxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 5/13/2010 10:09:45 AM
> Subject: [SI-LIST] Re: AC series capacitor position in high
speeddifferential signals
>
> Hmmm... I wonder how many of us trusts their measurements
> (blindly) without validating those? We all know that
> probing will have an effect on the results, especially at
> high speeds, right? Should I continue?
>
> Arpad
> =============================================================
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Lee Ritchey
> Sent: Thursday, May 13, 2010 11:28 AM
> To: Istvan Novak
> Cc: fei xue; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: AC series capacitor position in high
> speeddifferential signals
>
> 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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