If you have any of the PCB Design Conference proceedings for the last
few year find a copy of any of Rick Hartley's RF and High Speed
presentation they have some very good practical application
recommendations.
Jeffrey McGlaughlin, CID
Engineering Designer
Battelle
505 King Avenue
Columbus Ohio 43201-2693
(614)424-7582 Phone
(614)458-7582 Fax
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Babcock John
Sent: Thursday, September 14, 2006 12:13 PM
To: [log in to unmask]
Subject: Re: [DC] High-speed data converter grounding
Charles,
IEEE Press has a good book you may want to look at by Mark Montrose
"Printed Circuit Board Design Techniques for EMC Compliance"
It discusses techniques for grounding when you have mixed signals on one
board.
Also Howard Johnson books come to mind as well.
John Babcock, C.I.D.
www.spraycool.com
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Charles Gervasi
Sent: Thursday, September 14, 2006 9:06 AM
To: [log in to unmask]
Subject: [DC] High-speed data converter grounding
I'm wondering if anyone has any thoughts about the best place to tie
grounds in a design with high-speed data converters.
I am working on a software-defined radio that has high-speed ADC and
DAC, processor, FGPA, SDRAM, etc. This is all on a 2.7 x 2.2 in, 12
layer board. We are attempting to isolate the RF section, that is
everything on the analog side of the data converters, in an RF "can".
The "can" consists of a solid ground plane on layer 4, ground vias on
the sides, and a metal can on top of the (layer 1) RF components. The
"can" region accounts for a third of one side of the board. There are
digital components in all other areas of the board. The data converters
are located on the opposite side of the board (layer 12) near the can:
Question: Where is the best place to tie the analog (RF) and digital
grounds?
We think it should be at the data converters because data converters
expect a single solid ground.
BUT, most of the analog ground is located in the RF section on layers 1
through 4. Tying them on layer 11 under the data converters means we'll
have a little patch of ground on layer 11 for the data converters tied
to the digital ground on one side and tied by vias to the "can". This
intuitively doesn't sound like a good idea.
Does anyone know of good articles or books on grounding high-speed data
converters in very tight designs? This design is bound to take some
trial and error. I'm just trying to get the most mileage out of each
spin.
Thanks,
CJ
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