[SI-LIST] Re: Effect of Driving current
- From: "Ingraham, Andrew" <Andrew.Ingraham@xxxxxx>
- To: <ched_chang@xxxxxxxxxxx>
- Date: Tue, 14 May 2002 10:02:23 -0400
> I have a situation where an ASIC is connected to DDR-SDRAM.
> We have 2 IBIS models for the ASIC. The differences of the 2 IBIS
models
> are:
> - IBIS 1 has larger pullup and pulldown currents than IBIS 2.
> - IBIS 1 has faster rising and falling edges than IBIS 2.
...
> From here, there are too many unknowns.
>
> For example, one possible explanation is that your transmission line
> is resonant at the frequency at which you are using it, and then funny
> things like this can happen.
>
> Yes, the pullup and pulldown currents can affect the delay, but not
> necessarily in a simplistic way. It also depends on how you measure
> "delay", i.e., from what to what? Forget the old days when loads
> could be treated like lumped capacitors, and stronger drivers gave you
> less delay to charge up the load.
>
Andy
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