[sdiy] split ground plane

[ASSI]

On Montag 07 Juli 2008, Daniel Kruszyna wrote:
> I'm working on a pcb with separate analog and digital ground
> planes. Is there any special method I should use when routing
> signals from one side of the pcb to the other?

Split planes are a mixed blessing.  Their advantage is that you 
need not worry about the return paths between analog and digital 
getting into their way, but most cricuits are more complicated 
than that and require careful attention to the ground return 
anyway.

> For example, I 
> have an r2r on the digital side whose output I want to connect
> to a level-shifting opamp on the analog side. Is it ok to just
> route the signals between the two planes? Or does this method
> create a loop on the return path?

If the DAC is the only domain crossing, then you should connect 
the two planes at exactly that point.  You can use a choke for 
the connection as it should ideally just be a DC connection.  The 
two planes should never overlap, however, as that would AC couple 
them.  If you have them on two different layers, then you can use 
the digital ground plane layer for routing in the analog part and 
vice versa.


Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk]>+

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