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Arpad
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From: Muranyi, Arpad
Sent: Tuesday, April 26, 2016 9:07 AM
To: si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: Fwd: Impact of Double counting of clamp currents
Brijesh,
I wrote an article on this topic a long time ago. You
should be able to access it here:
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=403550
Note that this is not (only) talking about clamping at
the receiver, but also at the driver…
I hope this will answer your questions.
Thanks,
Arpad
=========================================================
From: Brijesh A Shah [mailto:shahbrijes@xxxxxxxxx] ;
Sent: Monday, April 25, 2016 10:43 PM
To: Tom Dagostino <tom@xxxxxxxxxxxxxxxxx>
Cc: Muranyi, Arpad <Arpad_Muranyi@xxxxxxxxxx>; si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: Fwd: Impact of Double counting of clamp currents
Thanks!! Arpad and Tom.
Arpad - Can you please share more details on scenario when ring back will
appear due to double counting of clamps? Can this be the case with output as
well as input buffer?
Best Regards,
Brijesh
On Mon, Apr 25, 2016 at 10:18 PM, Tom Dagostino <tom@xxxxxxxxxxxxxxxxx> wrote:
Brijesh
The amount of current that could flow in the clamps is related to the voltage
swing of the signal and the impedance of the trace supplying the signal to the
clamp. Let's say you have a full swing 3.3V CMOS driver (very low output
impedance) feeding a 50 Ohm line terminated with a 3.3V CMOS input. When the
signal gets to the open it will want to double and reflect back to the source
driver but the clamp will prevent the full 6.6V signal from ever forming.
Current will start to flow into the clamp. This current will be
(3.3V-V_forward)/50Ohms, or about 52mA max. If you look at the normal clamp
and double counted clamp IV characteristics you will likely find little
difference in the V_forward at that current.
Regards,
Tom Dagostino
971-279-5325
tom@xxxxxxxxxxxxxxxxx
Teraspeed Labs
9999 SW Wilshire Street
Suite 102
Portland, OR 97225
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Muranyi, Arpad
Sent: Monday, April 25, 2016 7:53 AM
To: shahbrijes@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Fwd: Impact of Double counting of clamp currents
Brijesh,
Strong clamping can have undesirable side effects, like "ringback", which is
the signal going back into the switching threshold region after a clamped
overshoot. I have seen cases when this would cause the input to detect
incorrect signal levels if it was sampled at the "right moment".
Thanks,
Arpad
====================================================================
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Brijesh A Shah
Sent: Monday, April 25, 2016 9:36 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Fwd: Impact of Double counting of clamp currents
Hi IBIS-Fans,
I have IBIS model with double counting of clamp currents, and without double
counting clamp currents.
In HSPICE simulations, I don’t see significant difference in
overshoot/undershoot due to double counting of clamp currents.
Did any of you observed the same? Or am I missing something? Is there any other
impact (except overshoot/undershoot) of double clamp current out of
the operating range?
Thanks,
Brijesh
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