[SI-LIST] Re: Impedance Controlled Board Production Vs Normal Board Production

  • From: "Todd Westerhoff" <twesterh@xxxxxxxxxx>
  • To: <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 05 Jan 2012 11:04:24 -0500 (EST)

... which is the fundamental point, isn't it?

<rant>

"How much impedance variance is acceptable?" is not an answerable
question, if the circuit isn't specified and the analysis isn't done.

Let me say that again - the original question is not answerable, based on
the data provided.  You want a rule of thumb for average situations?  Sure
- here you go.  You want to know if this rule will work in your situation?
No one knows.  

And while I'm on a rant, allow me to pose a few more unanswerable
questions:

        1. What's 2 + ?
        2. Which came first, the chicken or the egg?
        3. Why does the helicopter?
        4. What do you get when you cross an elephant with a rhinoceros?

I maintain that each of those questions is just as answerable as the
impedance tolerance question, with the exception of #4, which can be
answered.  The answer to that question is "elephino" (pronounced "elef eye
no").

</rant>

Todd.

-- 

Todd Westerhoff
VP, Software Products
SiSoft
6 Clock Tower Place, Suite 250
Maynard, MA 01754
(978) 461-0449 x24
twesterh@xxxxxxxxxx
www.sisoft.com


"It doesn't matter what you've heard
  Impossible is not a word
  It's just a reason
  For someone not to try"
                                                     -Kutless


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of DAVID CUTHBERT
Sent: Thursday, January 05, 2012 10:37 AM
To: Loyer, Jeff
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs Normal
Board Production

And you can simulate your circuit to explore how much T-line impedance
mismatch it can tolerate.
Dave Cuthbert
On Jan 5, 2012 8:24 AM, "Loyer, Jeff" <jeff.loyer@xxxxxxxxx> wrote:

> Perhaps I'm the only one who is finding it ironic that, on a "Signal 
> Integrity" reflector list, "Impedance Controlled" isn't considered 
> "Normal".  I haven't had the luxury of not specifying impedance 
> control since a small 33MHz PCI card design, many years ago.
>
> I'm afraid Jayasuryan that you won't find the answer you're looking 
> for on an e-mail thread, or it is going to be a long, drawn out, painful
affair.
>  You have a lot of work to do to understand what impedance control is 
> and how it relates to signal integrity.  I would recommend starting 
> with the books that have been listed many times on this list.  You can 
> also search the archives for "impedance control" to find discussions 
> about different opinions on how much is enough.
>
> Good luck in the new year,
> Jeff Loyer
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx 
> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of steve weir
> Sent: Monday, January 02, 2012 6:23 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs Normal 
> Board Production
>
> Suppose as you like.  Hope as you might.  What you don't contract is 
> not guaranteed.
>
> Steve.
> On 1/2/2012 5:56 AM, Jayasuryan KG wrote:
> > Dear Experts,
> >
> >
> >
> > Happy New Year!!
> >
> >
> >
> > I have question regarding the impedance controlled board production!
> > Is there any special process to produce impedance controlled board
> >
> > rather than the normal production?
> >
> >
> >
> > Suppose if I go with normal production for a  impedance controlled 
> > board
> (the design has been done to meet the impedance) what are the possible 
> issues can happen?
> >
> >
> >
> > Looking for your immediate response. Thanks in advance.
> >
> >
> >
> > Best Regards,
> >
> > - Jayasuryan
> >
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>
> --
> Steve Weir
> IPBLOX, LLC
> 150 N. Center St. #211
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>
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>
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