[SI-LIST] Re: stripline return paths etc.
- From: "Bharathan, Jayapratap" <jayapratap_b@xxxxxxxxxxx>
- To: <weirsp@xxxxxxxxxx>, <lalexman@xxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 6 Dec 2004 12:43:25 -0600
Hello all,
I have this general question with me. (I'm a beginner)
Suppose, if a High Frequency Signal Line is surrounded by a solid GND plane
on one side and a SPLIT GND plane on the other side, & supposing that the
solid GND plane is closer to the signal Line, the return path will be thru
the solid GND plane, since the High Frequency Signal takes the path of least
inductance (a smaller loop).
If this is the case, will it still matter if a high frequency signal Line
has a split plane next to it?
Thank you,
-JP
(Bharathan, Jayapratap)
----- Original Message -----
From: "steve weir" <weirsp@xxxxxxxxxx>
To: <lalexman@xxxxxx>; <si-list@xxxxxxxxxxxxx>
Sent: Monday, December 06, 2004 11:16 AM
Subject: [SI-LIST] Re: stripline return paths etc.
> Leonard, what you have with all the plane breaks is much more like a
> buried
> microstrip. The signal layer closer to the solid plane will exhibit
> higher
> impedance than a true stripline, and some modulation along the frequency
> axis. The signal layer closer to the split planes could look like a mess
> depending on several factors. You should avoid placing signals with high
> edge rates close to those splits. If you must run signals across the
> splits then bypass the splits with capacitors.
>
> It is all in the inductance. If you have a high inductance loop, between
> the two grounds, then you are setting yourself up for a lot of
> trouble. You really need to ask yourself, or whoever came up with this
> scheme what it is they are trying to do, and why those grounds need to be
> single pointed. You really ought to consider getting some expert help.
>
> Steve
> At 07:55 AM 12/6/2004 -0800, Leonard Alexman wrote:
>>Hi All,
>>I am designing many pcb's with multiple power and ground planes and I was
>>curious if some has an opinion or could point me to any articles on the
>>following questions.
>>
>>
>>1. I know its best to have a sold ground plane (or solid power
>>plane )
>>on either side of the a stripline trace but is it acceptable to have a
>>solid
>>ground plane on one side and a power plane on the other side with many
>>splits in the plane ? The same question for a dual stripline
>>configuration
>>?
>>
>>2. I have some high speed differential signals that have a separate
>>ground (HSGND). HSGND is tied to digital ground thru a zero ohm resistor.
>>I
>>am routing these signals in a stripline configuration with HSGND planes on
>>either side. Can I also route digital signals(that use the digital
>>ground )
>>on this layer ? I am concerned that the return path goes thru the zero ohm
>>resistor to the digital ground plane. and it will be a very long return
>>path. Is my assumption correct ?
>>
>>
>>Thanks for any help
>>
>>Leonard Alexman / American Electronics Group Inc.
>>PH: 951-354-6493
>>Cell: 951-640-5469
>>Fax: 208-247-33470
>>
>>
>>
>>-- Binary/unsupported file stripped by Ecartis --
>>-- Type: application/ms-tnef
>>-- File: winmail.dat
>>
>>
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