[SI-LIST] Re: PCB stackup
- From: "Ahmed Mubeen-W17666" <Mubeen.Ahmed@xxxxxxxxxxxx>
- To: <lnima@xxxxxxxxxx>, <s_aout@xxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 23 May 2006 15:36:28 -0400
Have some many power planes may hurt rather than helping. Having so many
power planes would give return current paths to signals that are of
different voltage level. This causes more EMI since you end up crossing
moats.
Also, do not want to have two different power fills on top of each
other.
It is better to calculate the total current needed by certain IC and run
thick traces (according to calculation) isolated from Clocks.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Nima Lotfi
Sent: Tuesday, May 23, 2006 12:31 PM
To: s_aout@xxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: PCB stackup=20
To minimize your radiation you may want to=3D20
1) ensure you have a low impedance power plane
2) be careful about shielding any cable grounds to your faraday =
case=3D20
"gnd".
To get a low impedance power plane you may want to consider having full
planes power planes, and a good decoupling strategy.
Also separation of ground plane to power plane plays a major role in
reducing power plane impedance. Use the minimum prepreg size that can
be supported for volume production.
As for cables that is a whole different story and I don't think it is
relevant to your situation.
Nima Lotfi
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
> Sent: Monday, February 21, 2005 3:03 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] PCB stackup
>=3D20
>=3D20
> Hi all,
>=3D20
> I am working on a product which requires high shielding (no =20
>interference with mobile pagers) and the PCB goes in plastic enclosure
>(w/o metallic paint). The highest working frequency is 200Mhz and the
>PCB stackup is :
>=3D20
> TOP ground
> Layer1 signal + power fill 1.8V
> Layer2 ground
> Layer3 signal + power fill 3.3V
> Layer 4 signal + power fill 5V
> Layer 5 ground
> Layer 6 signal + power fill 3.3V
> Bottom ground
>=3D20
>=3D20
> Is this stackup ok? and do you think that not having a full power =20
>plane would be a problem?
>=3D20
>=3D20
> thanks
>=3D20
>=3D20
>=3D20
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>=3D20
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