[sdiy] PCB GND planes layout advices needed...

[Jean-Pierre Desrochers]

> I see that you have two pins for ANALOG GND, what I would do in this case
> is dedicate one of the pins to "Quite Ground" and use that for
> the copper pour on both top and bottom. The quite ground should carry no
> current analog or digital and have a very low impedance to your ground
> "Star Point Connection". This will act as a classic ground shield
> design. 

Thanks Jerry for your very good advices.

That would force me to trace all the ANALOG GND paths to there
common power connector pin,  separately from the 'Quite Ground' right?
But that would leave lots of empty areas that the new QUITE GND
couldn't be able to fill...?? compared to a more spreaded
area covered by the ANALOG GND net itself..

Wouldn't it be good from your point of view to copper pour
both TOP and BOTTOM sides with ANALOG GND net (analog IC's area only)
but also copper pour both sides with DIGITAL GND only
in the digital areas separating both areas?


 On Mon 07/12/09 10:33 , "Jerry Gray-Eskue" jerryge at cableone.net sent:
> 
> 
> -----Original Message-----
> From: Jerry Gray-Eskue [jerryge@
> cableone.net]Sent: Monday, December 07, 2009 9:33 AM
> To: jpdesroc at o
> ricom.caSubject: RE: [sdiy] PCB GND planes layout advices needed...
> 
> 
> Jean-Pierre,
> 
> I see that you have two pins for ANALOG GND, what I would do in this case
> is dedicate one of the pins to "Quite Ground" and use that for
> the copper pour on both top and bottom. The quite ground should carry no
> current analog or digital and have a very low impedance to your ground
> "Star Point Connection". This will act as a classic ground shield
> design. 
> I would hesitate to use Digital and Analog ground planes on opposite sides
> of the board, this forms a low value capacitor and spikes may transfer to a
> degree between the ground planes. 
> Another common practice is to place all the digital and analog in separate
> sections of the board and use the corresponding ground for ground planes in
> each area. 
> Some of the most important design considerations for quite boards are using
> significantly larger tracks for power and ground traces, and spacing
> sensitive analog paths further from other tracks. The greater the gap
> between traces, the less capacitive and emf coupling of signal transitions.
> You can also use Guard Ring/Traces for sensitive analog traces and pin
> connections. In cases where I have a major noise source such as the system
> clock I may use a Digital ground guard trace to limit its radiated
> energy.
> - Jerry
> 
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl[synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Jean-PierreDesrochers
> Sent: Monday, December 07, 2009 8:07 AM
> To: s
> ynth-diy at dropmix.xs4all.nlSubject: [sdiy] PCB GND planes layout advices needed...
> 
> 
> 
> I need your advice on the following:
> I just completed the PCB layout of my new polyphonic (6 voices) MIDI2CV
> dotcom type module.It's a 7" X 8" 2 layers PCB. 
> I'm using a power connector with the following specs:
> 
> Molex 0.156" spacing
> Pin#     name
> 1         -15VDC
> 2         ANALOG GND
> 3         ANALOG GND
> 4         +15VDC
> 5         DIGITAL GND
> 6         +5VDC
> 
> Both ANALOG & DIGITAL GND's are wired  separately until they reach
> the remote power supply using different wire paths.
> There (and only there), they are wired together.
> 
> The board includes analog IC's (opamps, DAC's, transistors, etc..)
> and digital IC's (PIC microcontroller, gates, opto, etc..)
> Now that my OrCAD soft has helped me place
> both layer traces and since the ANALOG & DIGITAL grounds are 2 separate
> nets,I'm doing a 'copper pour' on the TOP side with
> the ANALOG GND net and a 'copper pour' on the BOTTOM side using the DIGITAL
> GND net.That's what are normally called GND planes..
> I know the actual TOP layer ANALOG GND generated plane will
> help a lot getting rid of noise all around the board, my question is:
> 
> Is it a good idea to generate a DIGITAL GND plane on the BOTTOM side
> tooor leave the DIGITAL GND paths not covering most of the BOT surface???
> (Remember ANALOG & DIGITAL GND'S are NOT wired together on the
> board)
> Thanks
> JP
> 
> 
> _______________________________________________
> Synth-diy mailing list
> S
> ynth-diy at dropmix.xs4all.nlhttp://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> 
> _______________________________________________
> Synth-diy mailing list
> S
> ynth-diy at dropmix.xs4all.nlhttp://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> 
>