[SI-LIST] Re: Analog/Digital Gnd
- From: James_R_Jones@xxxxxxxx
- To: parthsv@xxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Tue, 11 Mar 2003 14:54:58 -0600
For many systems, the analog section of the design is sensitive to noise.
Digital switching is inherently noisy. The reason that I have separated
these in the past is to keep the digital noise from coupling into the analog
subsection of the design. Digital noise can also couple into your analog
section via supply rails. That is the reason that these are kept isolated
as well.
Now here is more food for thought... Is it really necessary to separate the
analog and digital ground planes to achieve isolation? I have seen boards
where the analog section was on a corner of the board, and the rest was
digital. Now, since the analog section is not in the return current path of
any of the digital signals, is it really necessary to provide a plane break
for isolation? I tend to think that it would not really matter all that
much, and that it may be OK for the planes to coincide. Anyone ever tried
this?
James R. Jones
Dell
-----Original Message-----
From: Parthasarathy Sampath [mailto:parthsv@xxxxxxxxx]
Sent: Tuesday, March 11, 2003 2:44 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Analog/Digital Gnd
Hi All,
Why is that Analog ground and Digital ground are
kept seperate during Layout? I have even noticed in
some cases, seperate power rails are provided for
analog and digital block even though they require same
VDD.
Thanks in Advance,
Partha!
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