[SI-LIST] Re: How does multiple Ghz high speed signal behave on a sheet of conductor plane?

Dong,
Not to depress you, but it sounds like you are just starting out in Signal
Integrity, and you have a really large board (bad thing), and really high
speeds ( another bad thing).  Having the VRM 6 inches from the IC is just
the beginning of your problems.  You can have all the digital experience in
the world, and it won't help you here.  If you have any RF engineers that
you know, they might be able to get you farther down the road, but will
probably not be able to provide you with a solution.  You need a lot of
specialized expensive software, and a very experienced SI engineer behind
the wheel for a job of this type.  You are probably in over your head and
need to think about hiring a consultant.

Ken

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of steve weir
Sent: Thursday, June 21, 2007 10:02 PM
To: kimdongsik_us@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: How does multiple Ghz high speed signal behave on
a sheet of conductor plane?


Dong, bypass capacitance: in the die, as part of the PCB assembly and/or
the the IC package is all that can save you from the evils of
inductance. The DC/DC converter and its output capacitors becomes
largely irrelevant by about 1MHz.

Steve
Dong Kim wrote:
> My bottom-line effort is:
>   trying to minimize inductance between power source and a very high speed
switching component (multiple Ghz).
>   The 1 oz. power plane size is approximately 14”x12”.
>   The distance between the DC/DC power source to high speed switching IC
is about 6 inches.
>   The IC’s internal 256bit bus switching speed is greater than 3Ghz.
>
>   I am concerned about the high speed noise generated by the IC switching
feedback into the power source.
>   As the signal switching speed gets faster, I heard not only the skin
effect kicks-in but also the signal tends to flow straight, forming a narrow
strip path on the conductor sheet.
>   If the signal only flows thru the narrow strip of conductor, major
portion of the large sheet of conductor is no longer a good conductor for
the noise. It may just become an inductor in the high speed noise
perspective.  In another word, the large sheet of conductor is useless for
the effort of minimizing inductance.
>   Let me know if I am understood the concept straight.
>
>   Please advice me with your expert opinion.
>
>   Thanks
>
>   Dong Kim
>
>
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