Re: AC warning messages

Kim,

Ibischk3 figures out what voltage the buffer will settle at when
only the VI curves are used to drive the test loads. That is where
0.01V (pulldowm mode) and 2.37V (pullup mode) come from. The voltages
at the beginnings and ends of the waveforms should match these DC
levels.

Your second warning implies that the VI curves are delivering no
current at all. That makes sense to me, because ECL requires a
pullup, and this test fixture is giving it just a pulldown. Does
anyone know what the test fixtures should be for ECL?

Mike

Kim Helliwell wrote:
>
> When ibischk3 issues a warning like:
>
> WARNING - Model 'LVT162245_IO': TYP AC Rising Endpoints ( 0.01V, 2.45V) not within
> 0.049V (2%) of ( 0.01V, 2.37V) on VI curves for 50 Ohms to 0V
>
> where do the expected limits (0.01V, 2.37V) come from? The reason I ask is
> that I am getting a warning more like:
>
> WARNING - Model 'ECLout': TYP AC Rising Endpoints (-1.72V, -0.98V) not within
> 0.015V (2%) of (-2.00V, -2.00V) on VI curves for 50 Ohms to -2V
>
> where the upper and lower limits are the same, and that simply doesn't make sense.
>
> Also: how serious a problem is this? Do some or all simulators have problems with
> this sort of warning?
>
> --
> Kim Helliwell
> Senior CAE Engineer
> Acuson Corporation
> Phone: 650 694 5030 FAX: 650 943 7260
 
Received on Thu Oct 19 06:56:01 2000