[SI-LIST] Re: AC series capacitor position in high speeddifferentialsignals
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Steve Weir" <weirsi@xxxxxxxxxx>, "Peterson, James F (EHCOE)" <james.f.peterson@xxxxxxxxxxxxx>
- Date: Sat, 15 May 2010 08:26:47 -0700
Good point!
> [Original Message]
> From: steve weir <weirsi@xxxxxxxxxx>
> To: Peterson, James F (EHCOE) <james.f.peterson@xxxxxxxxxxxxx>
> Cc: <si-list@xxxxxxxxxxxxx>
> Date: 5/13/2010 10:56:53 AM
> Subject: [SI-LIST] Re: AC series capacitor position in high
speeddifferentialsignals
>
> I think the need for confirmation comes down to: What is the cost of
> failure? What is the likelihood of failure if a measure is not taken?
>
> Best Regards,
>
>
> Steve.
> Peterson, James F (EHCOE) wrote:
> > You need all three to align : theory (what we expect to see),
> > simulation, and measurement. It is only then that we can proceed
> > confidently into production. (I'm borrowing heavily from a DesignCon
> > panel discussion several years ago.)
> >
> > But we have to apply some engineering judgment to this approach. If
> > we're not trail-blazing, we have good design margin and good models,
> > maybe we can proceed without breadboarding. But if we are tight on
> > margin, it's a new technology, and our company's crown jewels are at
> > stake, then we need to make sure all three agree...
> >
> > Regard,
> > Jim Peterson
> > Honeywell
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Lee Ritchey
> > Sent: Thursday, May 13, 2010 1:25 PM
> > To: Muranyi, Arpad; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: AC series capacitor position in high
> > speeddifferential signals
> >
> > 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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>
> --
> Steve Weir
> IPBLOX, LLC
> 150 N. Center St. #211
> Reno, NV 89501
> www.ipblox.com
>
> (775) 299-4236 Business
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