[sdiy] analog or digital ground?

[harrybissell]

My call is think of where the currents involved want to return to... then
connect to the closest ground.

Latest Analog Devices seminar said they considered A/D, D/A etc mixed
signal to be ANALOG parts... they recommended some series resistors in the
digital inputs to limit current and let the gate capacitance of the device act as
a lowpass filter (hey its a couple pF....).   Sounded good to me.

Since you are switching the analog signals, I'd say analog ground.

H^) harry

Seb Francis wrote:

> Hi,
>
> I'm just routing the PCB for my MIDI2CV, and I've been pondering which ground plane to connect the S&H MUX to.
>
> It's a MAX306 (+/-V supply and analog signal range, TTL/CMOS compatible digital inputs).  Digital inputs come direct from a PIC (so they're pretty noisy).
>
> My first thought was to wire the GND pin to the digital ground (assuming there might be a bit of coupling to ground from the digital inputs), but the datasheet doesn't give much clue whether GND is in any way internally connected with the analog signal - the digital ground plane is itself a source of noise.
>
> Any thoughts?
>
> Seb