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ADC122S625 - to use in differential mode

Other Parts Discussed in Thread: ADC122S625, LMP7312, THS4531

Dear Sir,

I have basically 5v sine wave 15 khz signal with dc offset of 2.5 v & i want to measure signal using ADC122S625 using differential mode.

 

Plz suggest hardware to be used to convert this 5v signal to differential signal.

Regards

Atul Bhakay

  • Hi Atul,

    The simplest solution is to have the 5V sinusoid applied to the CHA+ input, 2.5V applied to the CHA- input and  VREF. Just make sure that 5V sinusiod source has low output impedance - may require buffering.

    In this configuration when CHA+ is at 5V, the output code will be Positive full scale ie 0x7FF; and when CHA+ is at 0V the output code will be negative full scale 0x800.

    This is a very compact and well performing solution.

    If the above is not a sufficient then you can use one of our differential OPAMPS to convert from single ended to the differential output. But here a few complicatioins loom:

    1. Increased complexity
    2. Limitations of the OPAMP output drive may force you to use multiple supplies; at least supplies above the ADC supply
    3. Increased cost

    The potential candidates are devices like LMP7312, or THS4531. Both devices' Data Sheets have sections on single ended to differential signal conversion.

    Sincerely,

    tom

  • Hi tom,

    I was not having account so Mr atul was posting on behalf of me.

    I understood what you said. i will prefer not to use differential amplifier.

    for VREF i will use buffered 2.5 instead voltage reference chip.

    the configuration you suggested like single ended configuration with dc shited ?  am I correct?

    if any query i will get back to you

    Thanks for reply 

  • Hi Santosh,

    I attached a PDF with the fundamental idea. 

    Keep in mind that depending on the output impedance of your sources, you may need to buffer both the signal (0-5V) and the DC source (2.5V to CHA- input, and VREF input).

    4645.ADC122 in general.pdf

    Sincerely,

     

    tom