Hi there, i'm designing the PCB for a DAC using a PCM179x (either 1798 or 1794a), and have a few questions regarding the layout of components I hope you may be able to help me with.
I'm largely referring to the application circuit (fig 23) in the 1794a datasheet;
1) Which components should be placed closest to the relevant pins:
1-1) the 0.1uF capacitors or the 10uF polarised capacitors (at Vcc2x). The (presumably old) 1794 EVM guide shows the polarised caps closer in the schematic, others show opposite.
1-2) Rf or Cf (to the pins of the IV op-amps)
1-3) the polarised caps for VcomX or for Vcc1
2) The PCM1798 datasheet shows a shared polarised cap for both Vcom pins. Presumably this primarily affects the channel separation. Is it possible to comment on how significant the effect of this would be on either chip? Would the improvement provided significantly outweigh the 'loss' from placing one of them further from the Vcom pins? (ie, the width of the capacitor further away)
3) how critical is the length of IoutXX paths to the op-amps? capacitor placement should take priority over significantly lengthening these traces?
4) is the 1798 capable of outputting the same 4.5V RMS stereo as the 1794a and does it share similar benefits? (ie. greater SNR)
5) Any advice RE: the preferred make up of the polarised 10uF capacitors or how critical this selection is WRT audio quality.
Thanks for reading.