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ADAU1372 ADC Polarity

I have programmed the ADAU1372 using the talkthrough mode and has configured the input as single-ended input with PGA powered down. I have injected a test audio signal for checking polarity and has discovered that the audio signal is inverted at the line output of the ADAU1372. The DAC is configured as normal polarity.

The datasheet states that single-ended input are not inverted and that the ADCs are non-inverting (see page 28). Why is it that the output that I observed on the oscilloscope is inverted? Is there an errata for this ADAU1372 or am I missing out on something?

  • Hello Wei Cheow,

    You are correct that the datasheet is exactly reversed from what the part actually does. The PGA does invert the signal but the ADC also inverts the signals so that the results when using the PGA is no polarity inversion. However, if you bypass the PGA then you will get a polarity inversion in the ADC.

    Thanks for bringing this to our attention. I will put in to make a change to the datasheet.

    Dave T

  • Hi,

    I also encountered the similar issue on the ADAU1772.

    ADAU1772 and ADAU1372, they have a lot in common except Fast DSP core, I understand.
    Does the ADAU1772's ADC also inverts the signals even if written as following?

                  ADAU1772 data sheet (rev.C)
                  Page 33 Signal Polarity
                  The ADCs are noninverting

    I found below.
    If the ADAU1772's ADC also invert the signals, the issue could occurs, I think.

                  Sign inversion ADAU1772

  • Hello Euglena,

    Yes, the parts are very similar so you would see the same thing on the 1772.

    Dave T

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