If the header has a separate "digital" ground for the 5V source, then
I don't see any reason to connect them on the PCB. The "star point"
is at the power supply. Many mixed-signal systems have analog and
digital grounds separated in this way, with the ground pins of the AD
and DA converters connected to the analog system ground. Putting a
ferrite bead or resistor between the grounds will create an impedance.
On 10/26/06, Adam Schabtach put forth:
>Question for Paul, mostly, but maybe others have considered the same thing:
>If I'm building a module from scratch, and I want it to play nicely with my
>MOTM modules (present and future), and it's drawing all three voltages
>through a MOTM-standard 6-pin power connector, and it's a hybrid
>analog/digital module, how do I connect together the digital ground and the
>analog ground on my PC board? It may be something of a moot point because
>AFAICT my Power-One triple supply has the grounds connected together anyway,
>but I'm wondering whether there is some little nicety that I should observe,
>like maybe using a ferrite bead instead of just plain copper.
>
>Thanks for any opinions or suggestions.