[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: PMC Spec - Characteristic Impedance Numbers?

>     Is there a proposal to set an impedance target for ... any of the
> other PCI module standards?
>     (PCI cards are 62 ohms..)
The unloaded characteristic impedance requirement for regular PCI add-in
cards is 60-100 ohms.  I have seen proposed ECRs that would change this
to 51-100 ohms (only when Cin of the IC on the end of the trace is <=
8pF), and an older one that suggested 50-70 ohms.

For PCI-X add-in cards, the corresponding requirement is 57 ohms +/- 10%
(51.3-62.7 ohms).  It extends lower than the PCI range for add-in cards,
but PCI-X also requires a smaller maximum device Cin.