PCM1822: Corrupted/Odd serial output

Thank you Garret, for the very quick response. I do want to be certain that I understand your comment. I have AC coupled the audio inputs already, through 10u capacitors. I have attached the entire audio input stage. I laid out the PCB pretty much directly as suggested in your data sheet.

As for the rest of the PCM1822 pins, the only inputs would be the BCLK and LRCLK timing signals, which I would not expect to be ac coupled.

My guess is that the problem lies elsewhere. However, it is serious for me and I am eager to solve it as quickly as possible. 

Can you clarify, or is there something else that I should look at?

Hi Mark,

I see, yes you are correct that the analog input pins are the only ones that should be AC coupled, which I now see you have done.

Is your IOVDD pin on the PCM1822 connected to the DSP? I can't seem to find the IOVDD label elsewhere on the schematic (I see the IOVDD pin 18 on the DSP is not labeled). Let's make sure this is connected to 3.3V before moving forward with the debug.

Best,

Garret

Interesting. I wil re-study my PCB to see if there's an error there. For the record pin 18 on the schematic is presently attached to gnd. That might create trouble.

Hi Mark,

I was referring to ADAU1701 pin 18 which is labeled IOVDD and externally connected to +3.3V. Meanwhile, PCM1822 pin 9 IOVDD is connected to "IOVDD" pin label, which is the one I suspect is not connected to 3.3V. This would cause errors in the data output from PCM1822.

Best,

Garret

Thank you for the great pickups. I will amend those today.

Before we consider this completely closed...: 

Everything works splendidly from a signals perspective. I did find, however, that the PCM1822 runs quite unexpectedly hot. It is soldered directly onto the main ground plane, and connected generously by suture vias to a bottom ground, and to an inner ground, all of which should dissipate heat quite well.

I haven't measured the temperature, but it is hot to the touch. Too hot, actually, to touch.

May I ask what my expectations should be about heat? Should I be concerned for the device lifespan?

Thank you.