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ads1211 problem

mehdi duman
Prodigy 40 points
Other Parts Discussed in Thread: ADS1211


We are using an anolog to digital converter called as ADS1211 in our project. However, a serious problem has been occured about this IC. Digital data ,which is read from ADS1211, changes with apporoximately one hundred seconds period and ten seconds duty cycle. Figure of it is attached below. We use two different system design for converting process but same problem was occured at both of them. Configuration settings that we used are like that:

Turbo mode: 1
Gain: 1
Data rate: 1000Hz,673Hz,100Hz
Reference: Internal , External
XClk: 10 MHz, 2MHz
Bias: Off
Data Format: Offset Binary
U/B : Unipolar
Operating Mode: Normal Mode


Could you give a feedback about this problem as soon as possible, please.


Best Regards



Mehdi Duman

R&D Engineer  TUBITAK SAGE


  • 0
    TI__Guru** 113765 points

    Mehdi,

    This is a rather substantial jump that could be related to input noise, supply noise, or reference noise.  I can't really tell what the vertical scale is so it is hard to determine how much variation there is in the measurement.  Is the vertical scale in codes?  What is the actual amount of change?  From the wave form it appears that something is switching on and off.  I would try to determine where the noise is getting into the measurement.  I would assume that the noise should be seen on either the inputs or the supplies with a scope.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 40 points

    Hi,

    This unexpected jump shown in the figure is about 100mV and it appears  with about one hundred seconds period. For example; in the beginning, the analog value that is given to the input pin by using power supply  is 1.5V. Then, after about one hundred seconds, it becomes 1.6V by itself and continues with this value about ten seconds. After that, suddenly, it decreases again 1.5V and so on. I saw this change from the oscilloscope. I think, digital data that is read from adc is correct and I think, there is something wrong in analog part.  On the other hand, I also checked the reference, Vdd and ground but I didn't see any problem during the alteration of the input voltage value.

  • 0 in reply to mehdi duman
    TI__Guru**** 181021 points

    Hi Medhi,

    We recieved an e-mail from our local field engineer regarding your issue, we'll work through Murat and post back here once we figure out whats going on in your setup.