[SI-LIST] Re: max transient current in target impedance calculation
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: "Wu, Jing" <Jing.Wu@xxxxxxxxxxxx>
- Date: Mon, 30 Jun 2008 08:56:53 -0400
Hi Jing,
Measuring the maximum transient current is not an easy task. For
generic designs, you may
be better off studying the nature of the load and make assumptions based
on its functions.
Sometimes the current fluctuations can be quite small percentage of the
maximum, for instance
if you have an array of high-speed links, which are always on and
running. In this case delta I
could be one percent of Imax or less. Another extreme is rails used only
for signal termination
purposes. If all lines are 'high' or 'low', it will create a full 100%
change in current so that
delta I = Imax.
Hope this helps.
Regards,
Istvan Novak
SUN Microsystems
Wu, Jing wrote:
> Hi, All:
>
> Could anyone clarify how to determine the max transient current in
> calculating the target impedance of PDS? Some people said the worst case
> I(t) curve first need to be generated and then FFT needs to be performed
> to get I(f) and finally Z(f) can be determined from Vrippl(f) and I(f).
> Some people said max transient current can be roughly estimated as half
> of the max current and max current can be determined from power
> consumption. Can the experts comment on different methods?
>
> Thanks,
> Jing
>
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