RE: [SI-LIST] : Split Plane

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From: Chung, Sinh (Sinh_Chung@littonas.com)
Date: Mon Apr 24 2000 - 14:03:32 PDT


Mike,

I have 10 layers on my board, I just used the four layers as an example why
I choose
to split up the Ref. plane.

What I tried to illustrate is that if the Ref. plane is split in two as
shown, my signals would be better
shielded. My signals are now shielded from above/below/and to the right with
GND. And they are all high speed digital signals.

> FOR EXAMPLE
>
> GND
> signal
> GND
> signal
>
> can be broken up as
>
> GND
> 1/2 signal 1/2 GND
> 1/2 GND 1/2 signal
> GND

-----Original Message-----
From: Degerstrom, Michael J. [mailto:degerstrom.michael@mayo.edu]
Sent: Monday, April 24, 2000 4:15 PM
To: si-list@silab.eng.sun.com
Subject: RE: [SI-LIST] : Split Plane

Sinh,

I don't think you've provided us with enough information.
Since you are using LVDS, which is differential, there
shouldn't be any problem with splitting the plane as long
as crosstalk between true/comp. pairs is kept in check.

There are two other things to consider assuming that
your board is only four layers as you defined below. First,
and others on this list know this far better than I, is that
your board (especially the first stack-up) may warp since your
your metal loading is not well balanced. Secondly, how do
bring in power? Depending on the rest of your circuitry,
you may have an AC power delivery problem since you
apparently have not provided a power plane.

Mike

_______________________________________________________________
Mike Degerstrom Email: degerstrom.michael@mayo.edu
Mayo Clinic
200 1st Street SW
Gugg. Bldg. RM 1042A Phone: (507) 284-3292
Rochester, MN 55905 FAX: (507) 284-9171
WWW: http://www.mayo.edu/sppdg/sppdg_home_page.html
_______________________________________________________________

> -----Original Message-----
> From: Chung, Sinh [mailto:Sinh_Chung@littonas.com]
> Sent: Thursday, April 20, 2000 5:54 PM
> To: 'si-list@silab.eng.sun.com'
> Subject: [SI-LIST] : Split Plane
>
>
> To Layout Experts,
>
> I'm wondering if anyone can offer some advice/opinions.
> I'm laying out a board where most of the critical LVDS signals
> are near the connectors but I cannot route all of them on the
> same layer.
> So therefore multiple layer is required, but they don't take
> up the entire
> layer since I
> want all the trace to be short, near the connector.
>
> I'm wondering if I split up the plane into two and make the
> other half gnd
> so that
> I can have more gnd and more layer to route my signals optimal signal
> integrity.
>
> FOR EXAMPLE
>
> GND
> signal
> GND
> signal
>
> can be broken up as
>
> GND
> 1/2 signal 1/2 GND
> 1/2 GND 1/2 signal
> GND
>
> My question is that by splitting up the layer, am I asking
> for trouble.
>
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