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ADS8866: About ADS8866's Gain Error

user4213425
Prodigy 20 points

Part Number: ADS8866

Tool/software:

Now, I am getting conversion results from an ADS8866 in 3-Wire nCS Mode under microcontroller control.

(SPI_COMM_MODE1 = CPOL=0, CPLA=1)

The gain error in the conversion results is 7%, which seems to be much larger than the actual performance stated in the data sheet.

Could you tell me what you think the possible causes are?

Best Regards.

  • 0
    TI__Genius 10797 points

    Hi Satoshi-san,

    Thanks for your question. At what temperature are you taking these measurements? Is your input signal single-ended or differential? What voltage? Could you share a schematic?

    Have you tried completing a 2-point gain error calibration? This video may help.

    Best regards,

    Samiha

  • 0 in reply to Samiha Sharif
    Prodigy 20 points

     - San,

    Thanks for your reply.

    I am so Sorry.
    Since the attachment of the image file fails, I will explain it in text.

    The evaluation circuit diagram is shown on page 1 of the data sheet provided by TI.
    VDDD=VDDA=REF=3.3V is applied from the regulated power supply.
    A bypass capacitor of 47uF is also included for GND.

    The input is a DC-Voltage of 100mV ~ 3200mV from AINP in 100mV steps form Voltage Source output direct.
    AINN=GND.

    I measured. For low input voltages, the error is small, but the larger the input, the error was larger.
    The AD conversion result  was measured 2996 mV when input = 3200mV.

    The environment temperature is 25°C.

    EG (Gain Error) = -0.01~+0.01 [%FS](TI Datasheet), but my measured result is about 7 [%FS].
    It seems very large.

    It would be helpful if you could tell us what factors are there.

    Best Regards.

  • 0 in reply to user4213425
    Prodigy 20 points

    I deeply apologize
    The cause was a mistake in data processing in my microcomputer.
    Solved.

  • 0 in reply to user4213425
    TI__Genius 10797 points

    Hi Satoshi-san,

    Thanks for letting us know! Good to hear the issue is resolved.

    Best regards,

    Samiha