Subject: Re: [IBIS-Users] Vinh for Differential Part
From: Timothy Coyle (Timothy.Coyle@nsc.com)
Date: Fri Dec 06 2002 - 10:14:55 PST
I think that most IBIS simulators use Vdiff as +/- of 0 V, assuming the
differential timing reference point is at 0V.
Regards,
Tim
|---------+---------------------------->
| | vinu@cisco.com |
| | |
| | 12/06/2002 12:29 |
| | PM |
| | |
|---------+---------------------------->
>------------------------------------------------------------------------------------------------------------------------------|
| |
| To: Timothy Coyle/Americas/NSC@NSC |
| cc: ibis-users@eda.org@Internet |
| Subject: Re: [IBIS-Users] Vinh for Differential Part |
>------------------------------------------------------------------------------------------------------------------------------|
Since these threshold voltages are used for timing measurements and since
datasheets specify timing at the zero crossing or Vddq/2 level, would it not
be better to set Vdiff=0, Vinl=Vinh=1.2V?
Thanks,
Vinu
Timothy Coyle wrote:
> Hello,
> I have a differential device in an IBIS file. I define a Vdiff of 100mV
> for my differential signal thresholds. However, I also have to define a
> Vinh and Vinl
> for the single-ended positive and negative differential Input model types
> in IBIS. The IBIS spec (3.2) states that:
>
> If a pin is a differential input pin, the differential input
> | threshold (vdiff) overrides and supersedes the need for Vinh
> | and Vinl.
>
> However, if I do not define a Vinh and Vinl for my differential inputs,
> then the IBIS parser gives me a warning. It also seems that some
> simulators use this
> Vinh and Vinl for the single-ended differential signals. If this is an LVDS
> input, switching from 1 to 1.4 V, then I could put thresholds of 1.1 and
> 1.3?
>
> I'm curious as to what other people do and why the parser gives me this
> warning?
>
> Regards,
> Tim
>
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