[SI-LIST] Re: Ring back

I don't think you'll find a definitive answer. =20

In Intel FSB specs, we talk about "positive ringback" (on rising edge)
and "negative ringback" (falling edge), but then we use the terms
"overshoot" and "undershoot" to describe similar phenomena with
different polarities.  (see
http://www.intel.com/design/pentiumii/datashts/24365703.pdf, page 40).
I don't know how other vendors use the terms.

I first hit this several years ago doing slot 2 designs and it's always
been counter-intuitive to me - I would prefer the terms "positive
overshoot" and "negative overshoot" instead of "overshoot" and
"undershoot".  But, there was too much momentum behind the existing
terminology to change it.  So, I've adapted my terminology accordingly.

To me, the bottom line is that these terms, like many in our discipline,
are merely conventions, and ambiguous ones at that.  It's best to very
carefully spell out exactly what we mean when using these terms (which
this spec does).

Likewise, even "stripline" is used to describe several similar
topologies - if there's an "absolutely correct" definition, it's
probably lost to history, and won't help you when someone else
misunderstands what you meant (regardless of whether you were correct or
not).=20

Obligatory Disclaimer:
The content of this message is my personal opinion only and although I
am an employee of Intel, the statements I make here in no way represent
Intel's position on the issue, nor am I authorized to speak on behalf of
Intel on this matter.

Jeff Loyer


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Aubrey_Sparkman@xxxxxxxx
Sent: Monday, May 22, 2006 11:40 AM
To: art_porter@xxxxxxxxxxx; leeritchey@xxxxxxxxxxxxx;
madhusudhan@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Ring back

Doesn't the concepts of over-damped (undershoot), under-damped
(ringback), and critically damped systems apply here?


Aubrey Sparkman=3D20
Enterprise Engineering Signal Integrity Team Dell, Inc.=3D20
Aubrey_Sparkman@xxxxxxxx=3D20
(512) 723-3592

The Greatest Pleasure in Life is Doing what People say can't be done...

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of art_porter@xxxxxxxxxxx
Sent: Monday, May 22, 2006 11:23 AM
To: leeritchey@xxxxxxxxxxxxx; madhusudhan@xxxxxxxxxx;
si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Ring back

I would argue that there is a difference. Undershoot is defined by the =
=3D
=3D3D IEEE in standard 181-2003 as "3.1.49 undershoot: A waveform
aberration =3D =3D3D within a post-transition aberration region or
pre-transition aberration =3D3D region that is less than the lower state
boundary for the associated =3D =3D3D state level." In layman's terms,
undershoot does not require a preceding =3D3D overshoot. Ringback to me,
again in simple laymans' terminology, is the =3D3D first (or lowest) dip
AFTER an initial overshoot. "Ringback" to =3D me =3D3D implies that =
there is
some resonance, so one would expect to see a =3D =3D3D damped sinusoid
following a transition.

There is no IEEE standard definition for "Ringback," but I believe it =
=3D
=3D3D has been defined in some semiconductor manufacturers' data sheets
and =3D =3D3D app notes. =3D3D20

Art Porter
Agilent Technologies =3D3D20

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
=3D3D On Behalf Of Lee Ritchey
Sent: Monday, May 22, 2006 9:02 AM
To: Madhusudhan Kulkarni; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Ring back

Ringback is just another name for undershoot.  I don't know why someone
=3D3D had to invent another name for something that already had a name.

When you have undershoot and you use series terminations, the terminator
value it too high or the output impedance of the driver is too high.  =
=3D
=3D3D When you have undershoot and you use parallel terminations, the
value of the terminator is too low.  Fix which ever problem you have by
changing the value appropriately.


> [Original Message]
> From: Madhusudhan Kulkarni <madhusudhan@xxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 5/22/2006 9:28:26 AM
> Subject: [SI-LIST] Ring back
>
> Hi,
> How to solve ringback problem and what is the disadvantages of =3D3D
ringback
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