[SI-LIST] Re: PDS simulation
- From: Istvan Novak <istvan.novak@xxxxxxx>
- To: John Kwan <jkwan@xxxxxxxxxxx>
- Date: Mon, 08 Jun 2009 23:30:13 -0400
John,
It might have been "open boundary" and/or "shorted boundary", referring
to components (or the lack of) along plane edges effectively shorting
the planes. 'Shorting' is relative: if components placed on the plane
represent an impedance at the particular frequency which is much less
than the characteristic impedance of the planes, they behave like shorts.
"Open circuit impedance" and/or "Short circuit impedance" may be the
terminology to describe how the planes (together with some of the PDN
components) can be described for certain functionalities. For instance,
good PDN should behave like open-circuited network when you consider the
active device connected to it. This simply means we expect that the
active load does not have a major impact on the PDN, or yet in other
words the PDN is 'stiff'.
People usually dont calculate the DC drop from the cavity impedances;
commercial tools can be used for this purpose which mesh the conductor
with sufficiently small cells to get the current distribution.
Self impedance (Z11 or Z22) is an important parameter when you are
interested in the noise generated locally at a noise source (active
device). Since a good PDN behaves like a low-pass filter, many times
this is the most important parameter. When ropagation of the noise
across the PDN can not be neglected, transfer impedance (or an
appropriate transfer parameter, such as Vout/Vin) should be used. For
instance, when you consider the noise from a DC-DC converter propagating
to an active device, the transfer parameter matters rather than the self
impedance.
Regards,
Istvan Novak
SUN Microsystems
John Kwan wrote:
> I heard people talking about "open circuit Impedance" and "short circuit
> Impedance" of the power plane of a PCB.
> Which one of them tells us about the impedance of the planes cavity?
>
> How do we tell the IR drop from this information?
>
> Why do we use Z11 and Z22 for the impedance rather than Z21 or Z12?
>
>
>
>
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