[SI-LIST] Re: Driver Impdance from IBIS
- From: steve weir <weirsi@xxxxxxxxxx>
- To: "Nijagunamurthy, Hithesh (GE Intelligent Platforms)" <hithesh@xxxxxx>
- Date: Tue, 14 Dec 2010 04:59:50 -0800
Driver resistance varies from a minimum at the start of a switching edge
when the voltage difference between the driver output and the
transmission line input is at a maximum to a maximum effective
resistance at the end of the switching edge when the voltage difference
is at its minimum. To derive approximate driver resistance you want to
take deltaV/deltaI near the center switching voltage.
Steve.
Nijagunamurthy, Hithesh (GE Intelligent Platforms) wrote:
> Hi All,
>
> How do you find the driver impedance information from the IBIS file.
> In the V/I table, is the listed voltage just V or Vcc- V
>
> The way I find impedance is
>
> For pull up -
>
> (Vcc-V in table)/I
>
> For pull down -
>
> (V in table)/(I in table)
>
> What voltage do you consider? 1.00 or 1.5?
> Some IBIS files mention if V in table is Vcc-V others don't.
>
>
> For PCI devices like power pc, Intel 21555 bridge, the impedance values
> I get is around 11 to 18 ohms.
>
> Thanks,
> -Hithesh
>
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