Subject: RE: [IBIS-Users] IBIS model Question.
From: whiz kid (we_r_frendz@yahoo.com)
Date: Thu Jul 11 2002 - 19:13:07 PDT
Hi Andy,
Thanks for the reply. In my case there is no AC
coupling capacitor. Its a point to point topology. I
simulated this with two different tools and I got the
same result.
Rahul.
--- "Ingraham, Andrew" <Andrew.Ingraham@hp.com> wrote:
> > I am running some simulations on a interface whose
> > swing is 800mv. when I simulate the wave forms
> that I
> > get have a swing from -400 mv to 400mv which
> obviously
> > is not correct.
>
> Why is it not correct? It sounds like the swing is
> what it's supposed to be.
>
> I'll guess that what you find wrong about it, is
> that the signal is symmetrical around 0V.
>
> > I was wondering as to what might be
> > the source of the problem in the IBIS models.
>
> Is there an AC coupling capacitor anywhere in your
> circuit? All SPICE-like simulators give misleading
> (but correct) initial results when doing TRANsient
> analysis of digital circuits with AC coupling
> capacitors. What the simulator simulated, is that
> the signal was inactive (at its t=0 state) for all
> negative time, then it suddenly starts switching.
> Thus, the charge across the capacitor might be
> different after a very long time of normal
> switching.
>
> If that is the case here, there is probably nothing
> wrong with your IBIS models. You can correct this
> by controlling the initial conditions, or by running
> the simulation for a very long time until the bias
> voltage across the capacitor can re-establish
> itself.
>
>
> > 2) The other question is pertaining to the IBIS
> model
> > convention. The signs for the current values in
> power
> > and gnd clamps. I see that the current values for
> the
> > Pwr clamp is positive and negative for gnd clamp.
> does
> > it mean that pwr clamp sources current and sinking
> > current for gnd clamp.
>
> IBIS current is positive when the direction is into
> the component. This is the standard in electrical
> engineering.
>
> When the applied voltage goes below Vss, the GND
> Clamp conducts and current flows out of the
> component, so the polarity of this current is
> negative. The GND Clamp sources current to the
> external circuit.
>
> When the applied voltage goes above Vdd, the POWER
> Clamp conducts and current flows into the component,
> so the polarity of this current is positive. The
> POWER Clamp sinks current from the external circuit.
>
> Regards,
> Andy
>
>
|------------------------------------------------------------------
> |For help or to subscribe/unsubscribe, email
> majordomo@eda.org
> |with just the appropriate command message(s) in the
> body:
> |
> | help
> | subscribe ibis <optional e-mail address,
> if different>
> | subscribe ibis-users <optional e-mail address,
> if different>
> | unsubscribe ibis <optional e-mail address,
> if different>
> | unsubscribe ibis-users <optional e-mail address,
> if different>
> |
> |or email a written request to ibis-request@eda.org.
> |
> |IBIS reflector archives exist under:
> |
> | http://www.eda.org/pub/ibis/email_archive/
> Recent
> | http://www.eda.org/pub/ibis/users_archive/
> Recent
> | http://www.eda.org/pub/ibis/email/
> E-mail since 1993
__________________________________________________
Do You Yahoo!?
Sign up for SBC Yahoo! Dial - First Month Free
http://sbc.yahoo.com
|------------------------------------------------------------------
|For help or to subscribe/unsubscribe, email majordomo@eda.org
|with just the appropriate command message(s) in the body:
|
| help
| subscribe ibis <optional e-mail address, if different>
| subscribe ibis-users <optional e-mail address, if different>
| unsubscribe ibis <optional e-mail address, if different>
| unsubscribe ibis-users <optional e-mail address, if different>
|
|or email a written request to ibis-request@eda.org.
|
|IBIS reflector archives exist under:
|
| http://www.eda.org/pub/ibis/email_archive/ Recent
| http://www.eda.org/pub/ibis/users_archive/ Recent
| http://www.eda.org/pub/ibis/email/ E-mail since 1993
This archive was generated by hypermail 2b28 : Thu Jul 11 2002 - 19:27:17 PDT