[SI-LIST] Re: add new power island in a 8 layer stack
- From: "Budathoki, Trilok (GE Consumer & Industrial)" <trilok.budathoki@xxxxxx>
- To: <calaf_calaf_calaf@xxxxxxxx>, <tbiggs@xxxxxxxxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 12 Jul 2004 11:45:07 +0530
Calaf,somtime back I have seen a board designed similarly to the =
costrains you mentioned.
It failed in EMI test.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Tom Biggs
Sent: Saturday, July 10, 2004 2:27 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: add new power island in a 8 layer stack
When you create a power island on a signal layer and you have two signal
layers between planes, then you might want to create an equivalent
ground island on the next layer (properly stitched to the ground plane).
This prevents auto-routed traces from crossing under this power island,
which would cause EMI and signal quality problems.
-tom
-----Original Message-----
From: steve weir [mailto:weirsp@xxxxxxxxxx]=3D20
Sent: Friday, July 09, 2004 1:46 PM
To: calaf_calaf_calaf@xxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: add new power island in a 8 layer stack
Calaf, when islanding power, power routing moves to signal layers and
only=3D20
the correct potential, usually ground is used for signal return planes.
To=3D20
avoid EMI problems, signals need contiguous returns. Digital ground =
is=3D20
digital ground. If you don't stitch your 2.5V and 1.2V returns together
you will have massive EMC and ground bounce problems.
Steve.
At 09:50 AM 7/9/2004 +0000, calaf_calaf_calaf wrote:
>Hi again,
>I do not get how adding and 2.5V power island in a signal plane. =
The=3D20
>fact is that I need four layers for power and gnd, and four layers =
for=3D20
>signal routing. Can I use any of the signal layers for such =
island?=3D20
>should I add a gnd island for that 2.5V island? Can I share gnd =
layer=3D20
>between 2.5V island and 1.2V layer? Can I separate one power plane =
in=3D20
>two layer or I should leave 3.3V plane in one layer and 1.2V plane =
in=3D20
>just another? Thank you for any help you can tell me
>Regards
>
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