[SI-LIST] Re: Analog & Digital Grounds
- From: Chris Adam <chris.adamsipi@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 9 Oct 2009 15:51:19 -0700
Thanks Lee and all those who offered valuable suggestions offline.
When do you really care to separate analog and digital grounds ? I see some
transceiver vendors recommend splitting the grounds while others don't.
Thanks,
- Chris.
On Fri, Oct 9, 2009 at 8:29 AM, Lee Ritchey <leeritchey@xxxxxxxxxxxxx>wrote:
> First of all, there is no sacred rule that analog ground and digital ground
> must be separate. Who knows where that came from. Use only one ground
> plane and manage the current flows so that digital ground currents don't
> flow under the area where the analog circuits are situated. It's pretty
> easy to do in most cases.
>
>
>
> > [Original Message]
> > From: Chris Adam <chris.adamsipi@xxxxxxxxx>
> > To: <si-list@xxxxxxxxxxxxx>
> > Date: 10/8/2009 5:47:35 PM
> > Subject: [SI-LIST] Analog & Digital Grounds
> >
> > I am working on a PCB design where number of layers is limited to 4 to
> > reduce cost. As opposed to the regular 'sacred rule', analog and digital
> > grounds are not separated though the respective VDDs are isolated. I am
> > particularly concerned that the merged ground is also a return path for
> > DDR2 signals. I would like to see how much noise does this ground
> merging
> > will introduce in sensitive power supply nodes such as for PLL and CDR.
> What
> > would be the appropriate simulation set up for this ? I am thinking of
> > multiport s-parameters, transfer impedance etc. I would appreciate if
> any
> > one shares his/her experience, thoughts and insights in this type of
> > analysis.
> >
> > - Chris
> >
> >
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>
>
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