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ADS8329: ADS8329 AD conversion value offset deviation

Atsushi Yamada
Prodigy 10 points
Part Number: ADS8329

Tool/software:

Hello forum members!


I am troubled by the phenomenon that the AD conversion result is offset in the + direction.
The following is an explanation of the situation.
The ADS8329 is operating in auto trigger mode.
3.3V is supplied to +VA and +VBD.
REF- is connected to GND and 3.0V is supplied to REF+.
Other peripheral circuits are set according to the recommended circuits (constants) in the data sheet.
Checking the AD conversion data obtained by the command “Dh”, a deviation equivalent to about 0.2V is generated.
For example, even if 0V is set between the +IN and -IN pins, the AD conversion value read out is “388”.
Is there any possible cause for the offset of the AD conversion value?
Please let us know if there are any items to check.

  • 0
    TI__Expert 6691 points

    Hi Yamada-san,

    Thanks for your question. Looking at the datasheet, it looks like the expected offset is closer to 2.5mV (plus additional offset drift error). The additional error may be a result of your signal chain. Are your supplies and reference the expected values when measured using a voltmeter/multimeter? If the offset is constant, the easier solution in this case would be to calibrate it out. 

    Here is a video that may be helpful: https://www.youtube.com/watch?v=zARSuyJtHYg

    Best regards,

    Samiha

  • 0 in reply to Samiha Sharif
    Prodigy 10 points

    Samiha-san

    Thank you for your response.
    In the REF voltage check you provided, we found that the actual voltage was off from the design value.
    Correcting the REF voltage solved the problem.

    Best regards,