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From: krw on 10 Jun 2010 19:17
On Thu, 10 Jun 2010 13:23:38 -0700 (PDT), Javad Benhangi <benhangi0(a)gmail.com>
wrote:

>The reason of using this stack up here is to isolate 600-700 Mbps
>signals that are in different layers.

You don't need a ground plane between planes to isolate them. If the signals
are orthogonal there will be little or no coupling. If the signals are a
fairly even density across the board the impedance will be fairly tight. A
plane on one side is almost always good enough.

>Ground planes are partly used as
>power planes because there is five different voltage levels and a
>single power plane isn�t enough for handling the power distribution.

Your English isn't very clear here, so perhaps we're talking past each
other... I would suggest having only one GROUND plane. The other full planes
can be used for power. The signals don't care whether the plane next to them
is power or ground (assuming sufficient bypassing, obviously). In any case
there is *no* reason to have a power and ground plane adjacent to each other.


>Anyway, how do you choose your stack up?

A number of ways to do it (it would have helped here if you hadn't
top-posted). Of course one would have to know a lot more about the board
(power, packages, layout).

If you're scared (and have deep pockets ;) and insist on 8-layers
Top: Signal-1 (most component footprints perhaps low speed wiring)
Signal-2
Ground
Signal-3
Power-1
Signal-4
Power-2
Signal-5 (decoupling opposite components)



Going cheaper (six layer):
Signal-1
Ground
Signal-2
Signal-3
Power
Signal-4



Top | Power Plane |
>> >Gnd1 | Mid1 | Gnd2 | Mid 2 signal | Gnd3 | Bottom

>Which software do you use?

I don't do layout, but the layout guy uses Allegro. The job I'm in now
doesn't have nearly the frequency requirements you do. I've been there,
though.

>Would you please introduce some good document/ application note to
>help me on designing the stack up on such high speed board?
>Many thanks

I've never seen anything useful. There's a lot of junk out there, though.

>> >The GN2 and Gnd3 layers are
>> >used for poser plane in some parts of the board that the high speed
>> >signals don?t exist.
>>
>> "Poser"?

You never answered the question about what a "poser plane" was.
From: Archimedes' Lever on 10 Jun 2010 19:26
On Thu, 10 Jun 2010 18:17:21 -0500, "krw(a)att.bizzzzzzzzzzzz"
<krw(a)att.bizzzzzzzzzzzz> wrote:

>You never answered the question about what a "poser plane" was.

One of the reasons you should not assist anyone.

It is obvious to anyone but the most retarded rib=poking dolt what he
meant. This from the idiot that calls his misspellings typos.
THIS was a typo. That fact is obvious, as is your stupidity for either
being blind to it, or using it to poke someone in the ribs with.

Either way, you are a loser for being that way.
From: Bill Sloman on 10 Jun 2010 20:27
On Jun 11, 1:17 am, "k...(a)att.bizzzzzzzzzzzz"
<k...(a)att.bizzzzzzzzzzzz> wrote:
> On Thu, 10 Jun 2010 13:23:38 -0700 (PDT), Javad Benhangi <benhan...(a)gmail..com>
> wrote:
>
> >The reason of using this stack up here is to isolate 600-700 Mbps
> >signals that are in different layers.
>
> You don't need a ground plane between planes to isolate them.  If the signals
> are orthogonal there will be little or no coupling.  

Unless of course all the signals in one bus change in the same
direction at the same time. This is a worst case situation, but it is
difficult to guarantee that it won't happen.

>If the signals are a
> fairly even density across the board the impedance will be fairly tight.  A
> plane on one side is almost always good enough.

For what kind of signals, with what kind of transistion times? Sloppy
habits that you can get away with at 100MHz can be fatal at 500MHz.

> >Ground planes are partly used as
> >power planes because there is five different voltage levels and a
> >single power plane isn t enough for handling the power distribution.
>
> Your English isn't very clear here, so perhaps we're talking past each
> other...  I would suggest having only one GROUND plane.  The other full planes
> can be used for power.  The signals don't care whether the plane next to them
> is power or ground (assuming sufficient bypassing, obviously).  In any case
> there is *no* reason to have a power and ground plane adjacent to each other.
>
> >Anyway, how do you choose your stack up?
>
> A number of ways to do it (it would have helped here if you hadn't
> top-posted).  Of course one would have to know a lot more about the board
> (power, packages, layout).
>
> If you're scared (and have deep pockets ;) and insist on 8-layers      
> Top:      Signal-1 (most component footprints perhaps low speed wiring)
>           Signal-2
>           Ground
>           Signal-3
>           Power-1
>           Signal-4
>           Power-2
>           Signal-5 (decoupling opposite components)
>
> Going cheaper (six layer):
>           Signal-1
>           Ground
>           Signal-2
>           Signal-3
>           Power
>           Signal-4
>
> Top | Power Plane |
>
> >> >Gnd1 | Mid1 | Gnd2 | Mid 2 signal | Gnd3 | Bottom
> >Which software do you use?
>
> I don't do layout, but the layout guy uses Allegro.  The job I'm in now
> doesn't have nearly the frequency requirements you do.  I've been there,
> though.

But aren't brave enough to say what sort of signal lvels you were
dealing with , or the signal transition times that your logic outputs
offered - as opposed to the rather slower transistion times that your
half-baked stack would have delivered to the logic inoytst that you
were driving.

> >Would you please introduce some good document/ application note to
> >help me on designing the stack up on such high speed board?
> >Many thanks
>
> I've never seen anything useful.  There's a lot of junk out there, though.

Your grasp of the subject doesn't suggest that you could reliably
distinguish the junk from the good stuff

In fact the Motorola (now ON-Semiconductor) ECL application notes were
fairly detailed, if somewhat over-simplified Fairchild and Philips
(now NXP) had similar application notes for their 100K and 300K ECL.

Howard Johnson and Martin Graham have written two books that address
the subject "High speed Digital Design" and "High Speed Signal
Propagation" (ISBN 0-13-395724-1 and ISBN )-13-084408-X respectively).
As John Larkin has mentioned, the books are poorly organised and not
as helpful as they might be, but they are better than nothing.

> >> >The GN2 and Gnd3 layers are
> >> >used for power plane in some parts of the board that the high speed
> >> >signals don?t exist.

Makes sense.

--
Bill Sloman, Nijmegen

From: krw on 10 Jun 2010 20:49
On Thu, 10 Jun 2010 16:26:25 -0700, Archimedes' Lever
<OneBigLever(a)InfiniteSeries.Org> wrote:

>On Thu, 10 Jun 2010 18:17:21 -0500, "krw(a)att.bizzzzzzzzzzzz"
><krw(a)att.bizzzzzzzzzzzz> wrote:
>
>>You never answered the question about what a "poser plane" was.
>
> One of the reasons you should not assist anyone.

Of course there is an obvious reason that you *can't*. You're *always* wrong,
AlwaysWrong.

> It is obvious to anyone but the most retarded rib=poking dolt what he
>meant. This from the idiot that calls his misspellings typos.
> THIS was a typo. That fact is obvious, as is your stupidity for either
>being blind to it, or using it to poke someone in the ribs with.
>
> Either way, you are a loser for being that way.

Why don't you go back and play in mommy's hamper and leave her computer alone,
AlwaysWrong?
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