AD7492 artifacts

Hello!

I am using the AD7492 ADC to convert an analog signal at about 0.1 MSPS but at irregular intervals I am getting single samples which are way off. The samples always contain many 1-bits near each other e.g. 0x3FF0 or oxE000. I have outputted the result to my computer downsampled to 5 kHz which is what is in the figure below.

The schematic is attached. I have also tried adding a 10 uF capacitor to the REF OUT analog reference voltage to no avail. I am new in this area so please bear with me if I have made some silly mistake.

output.pdf
  • 0
    •  Analog Employees 
    on Feb 2, 2017 6:03 PM

    Hi,

       I can see that you placed a 10uF cap in the refout pin. Would be able to replace it with a 100nF cap. The reference voltage is a critical component in the ADC conversion process. If the reference is unstable it is most likely that it will have an unstable conversion result. Please don't hesitate to ask if there are still problems.

    Regards,

    Jonathan

  • Hi,

    Thanks for the quick reply! I started out with a 100 nF capacitor only, as in the circuit diagram, but still had these problems (which is why i tried adding the capacitor). It is good to know that I should keep it as it was however.

  • 0
    •  Analog Employees 
    on Feb 6, 2017 1:27 AM

    Hi Lukas,

       In your result, it looks like the ADC output is good for a while and after some time, the result began to vary. The resulting conversion are near full scale, which means that changes are mostly on the lower bits of the code, although there was one spike on the result. I would like to ask, what is the resolution of the voltage source? Please make sure that the source is also grounded properly on your system. Can you try grounding your input? or a midscale voltage and we'll see if this flickering would exist. Please also make sure the power supply source are stable.

    Regards,

    Jonathan

  • 0
    •  Analog Employees 
    on Aug 2, 2018 3:43 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin