FreeLists / si-list / [SI-LIST] Re: true differential IBIS problem

["Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>]

B.R.

It is quite difficult in general to make an IBIS model=20
which is accurate when you float a bus.  The reason is
that very small currents can make a big difference in
the voltage to which it will float.  And I am talking
about nA or fA currents here.  I would even be cautious
about believing the SPICE models at these low current
levels.  For this reason, I would highly recommend=20
that you should use some design techniques which do
not rely on the accuracy of your models at such low
current levels.

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

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of TerenceHsieh@xxxxxxxxxxxx
Sent: Sunday, July 31, 2005 11:58 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] true differential IBIS problem

Dear All
I have generated a truly differential IBIS .But there are some problem.

When I generate the IBIS's rising/falling waveform, I use 50 ohm

for R_fix and common mode voltage for V_fix. In the sig-xp, if I use

the IBIS to drive a 50 ohm resistor terminated to common mode voltage,
the=20

waveform is exactly right .But I must use the IBIS to drive a
transmission

line without termination. When I use the IBIS to drive a pure
transmission

line the output waveform's DC level will change and common mode voltage
of=20

D+ and D- is different too .How could I generate a truly differential
IBIS=20

for pure transmission line network without termination?

=20

B.R.
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