[SI-LIST] Re: 6 layers stackup

Fernando,
The S1 S2 G P S3 S4 stackup can provide excellent power plane performance at
the expense of S1 and S4. Routing S1 and S4 mostly at right angles to S2 and
S3 can greatly reduce the crosstalk. And using narrow traces to maintain the
Z0 of S1 and S4 will take care of the Z0.

I often use S1 G S2 -  S3 P S4 for 6-layer boards. The signal traces are
nicely isolated with a 62 mil board having spacing like so:
10 mils, 5 mils, 22 mils, 5 mils, 10 mils. The tradeoff is that the power
plane Z0 is about 2X that of a board having 10 mils between each layer. The
power plane Z0 is still quite low with an inductance of about 200 pH per
square. Contrast this to an S1-G via inductance of about 300 pH and the
plane Z does not dominate things.

     Dave Cuthbert
     NARTE Certified EMC Engineer
     Consulting, SI, EMC, power electronics, analog of all kinds


On Wed, Feb 20, 2008 at 2:17 PM, Fernando Yuitiro Mori <mori@xxxxxxxxxxxxx>
wrote:

> Hi,
> I normally use S1 S2 G P S3 S4 for the 6 layers stackup. I need the 4
> layer with 60 ohms, so there are some problem if I use S1 G S2 S3 P S4?
>
> Regards,
>
> Fernando Mori
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