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RFGuest Post subject: Ground Planes? Posted: Mon Jan 23, 2006 5:15
pm Hi all! I was reading about ground planes and it seems like the
majority of the advice points to a design where two ground planes are
created for analog and digital signals and only connect them at one
point near the power supply. But I was reading some more articles and
noticed, this: "A number of different ground plane strategies
can be adopted for a radio product PCB. There is no unique answer to
the best strategy for a given type of product. Some people are great
advocates of split ground planes for analogue, digital, radio or audio
circuits. Experience on a number of radio products at Plextek has shown
that a single low impedance ground plane for all parts of the circuit
is usually a good starting point. Often attempts to split the ground
planes causes more problems than it solves. Careful consideration of
the flow of currents throughout the product is essential to minimise
digital interference with audio and radio circuits. Given the proliferation
in the use of DSP and microprocessors in radio products this is a very
significant issue." Can anyone comment from experience? Thanks!
Top Guest Post subject: Ground planesPosted: Tue
Jan 24, 2006 3:30 pm The major issue is how much non-DC current
flows in the ground region. I've had good results both ways,
but there are a couple of non-obvious (to most people) things to watch
out for: 1. Ground loops. If using separate ground planes, proper
("star") grounding becomes more significant. Ground loops can be hard
to avoid anyway, but can be critical for small-signal applications requiring
low noise pickup. 2. Proper bypassing. This reduces the difference
between the two configurations. There need to be both small, high-self-resonant-frequency
capacitors at the point of power use, the power plane/ground plane capacitance,
and a bulk capacitor as well. There's a lot of material about this on
the web - unfortunately, not all of it is correct. Watch out for unwanted
resonances. Basically, keep an eye on where the current is flowing.
Good Luck! Top IR Post subject: Posted: Wed
Jan 25, 2006 3:05 pm Site Admin Joined: Mon Jun 27,
2005 2:02 pm Posts: 373 Location: Germany Hello guest,
The issue that you raised is a very acute one. I had the same concerns
on my last PCB layout, which was for a large Mixed-Signal board with
close to 2000 components and included high-speed Digital sections and
RF sections up to 400MHz. What I did is using separate ground planes
for the Analogue/RF sections and digital sections and added optional
resistors at the schematic to connect between these planes. I connected
via holes from the different GND planes to the top layer and making
an option for connection between the planes through these resistors
if neccessary. Eventually I connected between the planes through
the resistors. Indeed, there is no one-way solution to this issue as
the 2nd guest mentioned in his reply. Therefore, you should make an
option in your layout to cover both options. Good luck!
_________________ Best regards, - IR Top
RFGuest Post subject: Posted: Wed Jan 25, 2006 5:37 pm
Thanks for the info! I've seen that term star grounding before.
Is that similar to starpoint ground? If so, can someone kindly explain
this? I am not familiar. Thanks! Top IR Post
subject: Posted: Wed Jan 25, 2006 5:57 pm Site Admin
Joined: Mon Jun 27, 2005 2:02 pm Posts: 373 Location: Germany
Hello RFGUest, Here is a link for you with relevant information:
https://www.aikenamps.com/StarGround.html Additional information
can be found by Google! _________________ Best regards,
- IR Top itsfrigid Post subject: Posted:
Sat Apr 01, 2006 5:13 pm Lieutenant Joined: Thu Mar 23,
2006 4:18 am Posts: 2 you might wanna have a look at the high
speed PCB layout seminar by analog devices - https://www.analog.com/en/content/0%2C28
... %2C00.html scroll down for this seminar.
Posted 11/12/2012
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