Okay, I understand that, and thanks for responding...
I was only curious about the difference between referencing to a GND vs. a
PWR plane

seeya,  Jack

        -----Original Message-----
        From:   Douglas McKean [SMTP:[log in to unmask]]
        Sent:   Tuesday, October 27, 1998 11:04 AM
        To:     [log in to unmask]
        Subject:        Re: [DC] Design for EMC
        Importance:     High

        At 09:58 AM 10/27/98 -0800, Olson, Jack C wrote:
        >
        >This may be a niave question,
        >but if Kirchoff's law states that for every current there is a
return
        >current, then it seems that everything that happens on a power
plane would
        >have a corresponding effect on the ground plane.
        >
        >So why is a ground plane any better reference plane than a power
plane?
        >(they are both "power planes" in effect?)
        >
        >Jack

        In short, unintended current flow.

        If you lay out the board with power and ground
        planes as you intend, these return paths *may*
        be unintended causing crosstalk to occur in
        apparently isolated circuits.

        As much as you want to keep power noise from
        getting into your circuits, you should also
        be aware of getting your circuit noise into
        your power circuits.  It's a two way street.
        I'm not sure that this is anything original.
        In fact, I'm not sure where I learned this.

        And also, this is strictly my own *preference*.

        ################################################################
        DesignerCouncil E-Mail Forum provided as a free service by IPC using
LISTSERV 1.8c
        ################################################################
        To subscribe/unsubscribe, send a message to [log in to unmask] with
following text in the body:
        To subscribe:   SUBSCRIBE DesignerCouncil <your full name>
        To unsubscribe:   SIGNOFF DesignerCouncil
        ################################################################
        Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
section for additional information.
        For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
        ################################################################

################################################################
DesignerCouncil E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE DesignerCouncil <your full name>
To unsubscribe:   SIGNOFF DesignerCouncil 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################