I have a question in regards to the ADAU1772. I want to use the codec in a DC coupled application with the converters. What I am trying to do is use the talkthrough mode of the part to pass the input from ADC0 to DAC0. I’ve made a few modifications to the board (eval board) too which include:
- Removing and shorting C2, C1
- Removed C34, R41
- Open J11
The idea was to remove the MICBIAS and use a DC coupled input with a 2.0V to 0V sensor. This looks like it should be well within the ADAU1772 ADC range with 0dB gain on the PGA; from the datasheet it looks like with VDD=3.3V it should be 2.54Vpp. For the purposes of experimentation I’m using a static 0.85V supply to drive the input of the ADC.
I am trying to output this to DAC0 (which I’m guessing is HPOUTLP/LOUTLP). I configured the part in SigmaStudio to be in talkthrough mode. I made no other changes to the ADAU1772 DAC output (it looks like I shouldn’t need to).
I can’t seem to get anything out of the DAC. Did I miss something obvious; attached is my SigmaStudio program. I expected with the gains all set to 0dB on the PGA, and 0dB on the DAC that I should see basically the same input from the ADC back on the DAC (with some added errors but still pretty close).
Any feedback into what i have missed is apprecaited.