Hello, I´m building S/PDIF DAC with PCM1794A and I have some questions about capacitors on PCM1794s
analog side and bypass with smaller capacitor and ground below current outputs.
1.)
This DAC has a lot of analog grounds and a lot of different Vcc pins. I have not found detailed information about where is the best place for positioniong each capacitor.
Pin28 and pin27 have decoupling capacitors 10uF+0,1uF. Pin 15 and pin16 have also its decoupling capacitors 10uF+0,1uF. It is very logical.
In topic "PCM1792 performance issues" is other good informations:
"Decoupling capacitors for pin21 and pin22 should connect pin23 directly with shortest pattern"
"10k ohms Resistor for pin20 should connect pin19 directly without using GND plane"
I still do not know where is the best position for third 10uF decoupling capacitor. I am thinking its ground. To pin24? or pin19? or ideally connected both pin19 and pin24 in closest position as possible?
[img]imageshack.cz/.../TIprintscreen.jpg[/img]
I have ground layed on Top PCB side and bottom side, but close position of the components near the DAC
makes from ground thin wires, which i would like to know, where should be this connected. Bottom layer
is without holes, but it has to have long VIA to connect to the upper layer.
2.)
Does any of the capacitors, which does not have bypass in the datasheet (47uF,47uF,10uF), for correct function
any bypass? 100N ceramic capacitors.
3.)
Theoretically, does the ground under the power outputs of DAC have any influence on THD? Is it better
to have ground under the outputs or cut the ground under them? Im working with LM6171.
That is all, thanks. And sorry for my english I hope that my post is readable.
