[SI-LIST] Re: LC filters on power pins
- From: "Jim Muccioli" <james@xxxxxxx>
- To: <david.kaiser@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 27 Sep 2001 15:09:05 -0400
Hi David,
I agree that the standard filter components are proving ineffective at Gbit
speeds.
However, we finally have data on the X2Y structure in ferrite that does show
effectiveness (IL of 80db @ 1MHz and 27dB @ 6GHz). More needs to be researched
but we
feel by combining the ferrite material and the bypass circuit attachment, these
ferrite
components will offer broadband filtering with low signal distortion.
You can access the IL data and a preliminary ITEM Magazine Article showing
other data at
these links:
IL Data
http://www.x2y.com/cube/x2y.nsf/(files)/FerriteTest.pdf/$FILE/FerriteTest.pdf
ITEM Article http://www.x2y.com/cube/x2y.nsf/(files)/Item.pdf/$FILE/Item.pdf
Best Regards, Jim
X2Y
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of David Kaiser
> Sent: Thursday, September 27, 2001 12:14 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] LC filters on power pins
>
>
>
> I have a question about LC filters on power SERDES and other Gbit devices.
>
> Most SERDES venders provide app notes that suggests using LC filters on the
> power pins of these Gbit devices to prevent noise from getting on to the
> power planes. But it seems to me that the LC filter components would have no
> effect at these Gbit frequencies, and could in fact make matter worse
> because the power pins would have no more than maybe a small island of
> interplane capacitance for decoupling. It seems that it would be better to
> just tie the power pins directly to buired capacitance planes. What do the
> SI gurus think?
>
> Also, it seems that at multiple GHz frequencies, the return path for the
> noise on the power planes would be so short, that noise would be squelched
> to quickly to cause problems on the planes.
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