[sdiy] Various GND planes in PCB layout..

[jays at aracnet.com]

Bert,

I don't know if I would put an inductor on the ground. What I've done before when working with audio converters is the following:

1) Connect the digital and analog ground at one and only one point. Make sure the trace is big enough to handle the current. Put this near where the power comes into the board and before it is used by the digital section.

2) The system that I was working with shared +5V for both the analog and digital components on the board. The primary was analog +5V. To get the digital +5V we would use either a ferrite or a small value resistor (10 to 20 ohms) between the analog and digital +5V. Then we would bypass the +5 at the resistor or ferrite with a larger value cap (4.7uf to 22uf) and each digital chip had a smaller 0.1uf bypass cap. Also make sure the resistor/ferrite can handle the current.

Might want to get some of the application notes and/or audio converter data sheets from Analog Devices, Crystal or AKM and check out their PCB layout notes.

Jay S.

Bert Schiettecatte wrote:

> Hi all,
> 
> I'm still working on a PCB layout here, and there is some digital stuff
> on it as well as analog stuff (opamps, etc). I thought it was a good
> idea to give the analog sections their own ground plane, and connect the
> ground and power to the rest of the circuit through an inductor (1.2uH).
> Is this a good idea? Should I use something else instead of an inductor?
> What about a ferrite bead? How do people connect ground planes of
> different sections of a pcb layout?
> 
> A big thank you to all the people who responded to my question about the
> mic preamp! If you ever make it to Belgium, there will be some cold beer
> waiting ...
> 
> Thanks!
> bert