Digital audio and seperate power supplies

[Zero Cool]

I am trying to gain some understanding of what the important facts are regarding power supplies and digital audio and let me explain what I mean by that a bit farther.

I am building a DAC using dual PCM1794A DAC chips, a CS8416 Mux and a USB board.

So looking at the power supply requirements for the PCM1794A chips:

http://www.ti.com/lit/gpn/pcm1794a

We find that the 1794A has FOUR power supply pins.

Vcc1 - Analog 5V power supply
Vcc2L - Analog 5V (L-Chan DACFF)
Vcc2R - Analog 5V (R-Chan DACFF)
Vdd - Digital 3.3V supply

So I would think obviously we would want to separate the digital and analog supplies. not only because of the different voltages, but to keep digital noise out of the analog supply lines.

Now is there any reason why the three analog 5 volt supply lines should be separate? even a minute amount of channel separation or lowered noise floor etc?

and if there is a reason too, can we use one transformer winding, bridge, cap bank and then just use 3 voltage regulators? or do we need separate transformer windings for each?

I would imagine the 3.3V Digital line would want its own winding? or can that too be run off the same winding as the 5V analog lines?


lets discuss.

Zc

[nigelwright7557]

I would use seperate regulators but a common winding.

[Zero Cool]

for the analog and digital too?

[qusp]

definitely use the same winding for all the analogue supplies, separate regs, but they should have a common ground referrence, i would also run the XO from the same winding, the dac internal analogue reference, analogue output stage and the oscillator should all connect to exactly the save ground potential, even star grounding from different tx could produce enough variance to effect performance

[twest820]

Originally Posted by Zero Cool

ets discuss

What are you looking to achieve that the EVM layout doesn't?