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ADS8689: Connecting the INA129 instrument amplifier IC to ADS8689

MESH
Intellectual 880 points
Part Number: ADS8689
Other Parts Discussed in Thread: INA129

Hello,

I considering analog input circuit board that uses ADS8689.

I am thinking of connecting the INA129 instrumentation amplifier IC to the AIN_P pin of the ADS8689.
(The INA129 outputs signals is DC to 10kHz)

Please let us know if you have any knowledge about the compatibility between ADS8689 and INA129.

I have experienced troubles with the compatibility between another AD converter and another amplifier circuit in the past, so I have confirmed the above just in case.

Regards,
MESH

  • 0
    Intellectual 880 points

    The details of the trouble at that time are as follows.

    - It took a long time for the input signal of the AD converter to stabilize.
    - As a result of replacing it with another amplifier IC, the time until the signal stabilizes has been dramatically shortened.

    MESH

  • 0 in reply to MESH
    TI__Mastermind 42285 points

    Hi MESH,

    ADS8689 does not fit your requirements well because this ADC has an internal LPF which has a 15kHz BW, so your high frequency signal (10kHz etc.) will be attenuated and distorted, see the magnitude response in Figure 7-5 in the datasheet. You need a ADC with a higher BW filter or without a filter. What's your signal range/type? what's your gain on INA129? What's the ADC sampling rate you need?

    Regards,

    Dale

  • 0 in reply to Dale Li
    Intellectual 880 points

    Hi Dale,

    Thank you for your reply.

    There is an error in my text.

    Correct: The INA129 outputs signals is DC to 1kHz

    Error: The INA129 outputs signals is DC to 10kHz

    *** Additional information ***

    Signal range: -9.5V to +9.5V.

    Signal type: sin wave.

    ADC sampling rate: 3kHz

    Regards,

    MESH

  • 0 in reply to MESH
    TI__Mastermind 42285 points

    Hi MESH,

    Is your signal a differential signal? Are you planning to configure your INA129 with G=1? 

    The ADC sampling you are planning to use is too low because you will only get 3 samples per cycle.

    Regards,

    Dale

  • 0 in reply to Dale Li
    Intellectual 880 points

    Hi Dale,

    Input of INA129 is differential signal.

    Gain of INA129 is 1.

    I rethink about the sampling rate.

    Regards,

    MESH

  • +1 in reply to MESH
    TI__Mastermind 42285 points

    Hi MESH,

    I do not think there is any potential issue using INA129 with ADS8689. I can help to review your schematic when you finish and share it.

    Thanks&regards,

    Dale

  • 0 in reply to Dale Li
    Intellectual 880 points

    Hi Dale,

    Thank you for your reply.

    I will design a circuit that combines ADS8689 and INA129.  

    In the process of my circuit design, if I encounter additional questions about the ADS8689, please let me know.

    Regards,

    MESH