RE: question on Tflight

> i have a question on Tflight
> when i am measuring Tflight b/n processor and 440bx both for fast and
> slow
> corner,
> i am getting Tflight_min (fastcorner) value more than Tflight_max
> (slowcorner).
> I am measuring Tflight as per guide lines.
> can i get like that ?
 
I am not sure if this is relevant to your question; I don't know whose
"guidelines" you are using; etc.

But if you define Tflight as the difference between the signal at the far
end of your actual trace, and the transmitted signal with a standard test
load, this can happen, especially if the test load is capacitive. (Doing it
this way makes it easier to add the driver's datasheet delay to Tflight, and
the result is the total delay to the receiver's input.)

In the slow corner case, the driving device's delay into the standard test
load is more, so it is a larger number that you subtract from the total
delay to get Tflight. If the test load is highly capacitive, it can
exaggerate this effect, causing the delay with the test load to become
larger at a faster rate than that with your real load. You can even get
negative "wire" delays this way, especially in the slow corner case.

Regards,
Andy

 
Received on Tue Apr 17 08:41:56 2001