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ADS1146: ADS1146 application issue

Jason Fan
Intellectual 1705 points
Part Number: ADS1146
Other Parts Discussed in Thread: ADS1120

Hi  Experts:

               My customer would like to use the ADS1146 in their system,  the ADS1146 is supplied by the unipolar power supply but the differential input is the pure

AC signal without the DC-offset , according to the equation3 in the d/s , the common-mode input voltage of each input should be subjective to the range below :

because the VCM is equal to zero (pure differential AC signal) , it does violate the range .

             Is there any solution to resolve ? For example , add the DC-blocking capacitor on each of the input ?

  • 0
    TI__Guru* 97575 points
    Jason,


    The ADS1146 wasn't designed to operate with an AC coupled input. The input signal needs something to establish a DC common-mode point within the ADC input range. I don't think that using a simple DC blocking cap will work.

    If they need to use a device that has an absolute input range that goes to ground with a unipolar supply, I'd recommend the ADS1120 as a replacement. It has a feature that bypasses the PGA, and allows for an analog input to be connected to ground. Even while bypassing the PGA, the ADC is still capable of a gain of 1, 2, or 4.


    Joseph Wu
  • 0 in reply to Joseph Wu
    TI__Intellectual 1705 points

    Hi  Wu:

              Thanks for your comments, actually , the input signal is AC coupled input (the absolute input is below the ground).

               Can I find a method to bias the input signal ?

  • 0 in reply to Jason Fan
    TI__Guru* 97575 points
    Jason,


    What is your customer measuring? It may be more helpful to describe the sensor measurement and then figure out how the circuit should be set up. A circuit diagram may be helpful.


    Joseph Wu