DC measurement with ADAU1961

Hello,

The ADAU1961 was designed to convert audio signals, but we have a sensor where we have to measure a DC-Signal. Ist this also possible with the ADAU1961?

Thank you for your help!

Regards,
Josef Peter Gessler | Embedded SW Engineer |

  • 0
    •  Analog Employees 
    on Oct 14, 2015 7:37 PM

    Hello Josef,

    It is possible but not simple. The inputs are biased up to the common mode voltage of the part. This is available on the CM pin. With audio the signal should be cap coupled to avoid pulling down or up the CM voltage. I am not sure on this part if pulling down the CM voltage on the input pin would affect the other pins in the part. I do not think so but it is worth testing. However, Pulling down the CM pin would affect the reference for the entire part.

    Then there is the issue of number format. The I2S output will be in 2's compliment form so any voltage below the CM reference voltage will produce a negative number.

    The last issue is that the part does use Sigma-Delta converters so for a DC signal you will not get full resolution. You will probably only see 16 bit resolution at the most and maybe a little less.

    Let me know how it goes if you try it.

    Thanks,

    Dave T


  • One relatively simple way to do this would be to use some analog switches to chop the DC signal. You can then AC couple and feed the generated square wave to the ADC and compute the DC value from the peak to peak readings.

    Klaus

  • Sorry, but I dont understand,

    Why will there be less than 16-bit Resolution if I use the SD-Converter for DC-Measurement?

    Thank you for your response!

    regards,

    Josef

  • 0
    •  Analog Employees 
    on Aug 2, 2018 3:13 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin