[SI-LIST] Re: Strange Gnd Clamp V-I curve when generating IBIS

  • From: "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>
  • To: <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 16 Dec 2004 16:45:43 -0800

Just a word of caution.  It is true that currents in the uA
and nA range may not put a big dent into your normal signal
integrity simulation results (when buffers are driving and
receiving).  However, there are some folks out there who may
be interested in how the bus floats, i.e. what will the
voltage on a bus be when all buffers are in the high impedance
state.  In this case even these small currents become important.

It is the model maker's choice whether they want to make their
IBIS model accurate enough for such purposes by making sure
that the clamp tables do have these currents in them.

Arpad Muranyi
Intel Corporation
-----------------------------------------------------------


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of Tom Dagostino
Sent: Thursday, December 16, 2004 11:39 AM
To: Rohan.Hubli@xxxxxxxxxxxxxxxx; a.ingraham@xxxxxxxx; =
si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Strange Gnd Clamp V-I curve when generating IBIS=20

Most datasheets will spec input leakage currents at less than 10 uA.  =
This
is supposed to account for the leakage currents.  If you have less than =
that
I wouldn't worry about it.  10 uA and 50 Ohms gives 0.5 mV of IR drop
assuming you have a 50 Ohm termination in the system.

If you don't like seeing that current you can zero it out and not really
change the model.

Tom Dagostino
Teraspeed Consulting Group LLC
503-430-1065
tom@xxxxxxxxxxxxx
www.teraspeed.com
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