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ADS1256: Error at PGA Gains of 32 & 64

lei cheng
Prodigy 10 points
Other Parts Discussed in Thread: ADS1256

Hi

I am a user of ADS1256. Now I have some problems in its PGA setting. Here is the phenomenon. I use the differential input mode, and I attach AINn to AIN0 and AGND, AINp to AIN1 and 40mv. When the PGA =1,2,4,8,16, the outputs were right, but when the PGA=32 or 64 the outputs are 76mv and 1050mv not 1280mv and 2560mv. And this time the noise was very large. I cannot find the reason please help me, think you!

  • 0
    TI__Mastermind 44720 points

    Hi Lei,

    Welcome to the TI E2E forums! From your description I'm not sure you are getting the bad results.

    Are you enabling the PGA buffer?

    The buffer limits the absolute input range to the ADC. However, if your inputs are 0V and 40mV, I don't see an issue when using the buffer.

    Is your ground really 0V or the same as the ADC's AGND?

    If the AIN0 to AGND connection is done with a jumper wire and on a breadboard, you may be introducing parasitics into your circuit and measuring something other than what your expecting. Try probing AIN0 and AGND and see if there is a difference in voltage potential (it may be more than just a DC voltage potential).

    Is it possible the ADS1256 is getting reset at some point and measuring AIN0-AIN1 (default), instead of AIN1-AIN0?

    Do you have a schematic you could share with me?

    Best Regards,
    Chris