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ADS1232, Glitch in the input signal

YongJie Chai
Prodigy 210 points
Other Parts Discussed in Thread: ADS1232

 

A consent current is directed to follow through a resistor and we are measuring the adc across the resistor terminals, there for we must get a clean dc signal constantly. But for some reason we are getting the glitch in the signal, but if the ADC is isolated the glitch is no more present
  • 0
    TI__Guru**** 180961 points

    Hi YougJie,

    Can you provide more detail?  Perhaps a schematic of your analog input and ADC connections along with details on the glitch?  What do you do to isolate the ADC?

  • 0
    TI__Guru* 97775 points

    YongJie,

    Tom is correct, we will need more information to help diagnose this problem.

    However I have seen some information (as was sent to our FAE), although I have not yet seen the schematic.

    The glitches that you see are very large so you should be able to track them down. It looks like you are measuring a 600mV signal. How is this generated? On the scope, the glitch is seen on the AINN and AINP lines, so it does not look like the ADS1232 that is causing this problem.

    First, look at the input. I know that you have some sort of opamp buffer, and an RC low pass filter. What values are you using for the R and C? Do the RC time constant match with the glitch that you see? What is on the input side of the buffer? Do you have any sort of glitching on the power supplies? Or is there any glitching on the source?

    I will try to request the schematic from the FAE, if you do not want to post it here.

    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Guru* 97775 points

    YongJie,

    I did get a copy of the schematic but I don't see anything that would normally be a problem.

    In addition to my questions though, I did have two others:

    1. How often do the glitches come up? Do they come up at a normal frequency?

    2. Have you looked at the reference as a source of noise? Since this is used to generate the input voltage, you should look at this to check for any glitches.

    Joseph Wu

  • 0 in reply to Joseph Wu
    TI__Guru**** 180961 points

    We were able to verify that the glitch in the input signal was coincident with the changing of the MUX.  As more information becomes available, we'll post any pertinent tips and tricks to help others who may have similar problems.