AD7641 EVAL Board clipping and software issues

Dear all,

I have set up the EVAL-AD76XXEDZ with the AD7641 and the EVAL-CED1Z. When I am trying to measure a signal with the EVAL-PulSAR-CED software, I am getting this output:

The signal parameters are:

  • AWG: Agilent 33120A
  • Vpp = 5,063V
  • V_Offset = -1,2V
  • f = 40,4Hz
  • CLOCK: INT. (EvalBoard)
  • The second differential input is connected to AGND

My questions are:

  What is the reason for the "clipping" at approx. 1,5V?

And consequently:

  1. How reliable is the Eval PulSAR-CED.vi-software? (I think there have occured some differences between the spectrum and scope waveform)
  2. Are there any possibilities to get the pure digital codes quickly?

Thanks a lot in advance
Best regards
Matthias

  • 0
    •  Analog Employees 
    on Feb 15, 2017 9:19 PM over 4 years ago

    Hi Matthias,

    What reference voltage are you using internal or external?. Make sure you’re not  violating the analog input range  of AD7641 from 0-2.5V and input signal  must  be antiphase around vref/2.In your case the other analog input is connected to  GND which violate the restriction. This affects the  result in the Eval software  you’re getting, specially putting one analog  input to GND in a differential ADC. I would suggest to change to a Pseudo- Diff part like we recently released the AD4000 or to use a fully differential amplifier like the ADA4932 to do the SE to Diff conversion before the AD7641. If you want a 2MSPS 18bit part you can also look at AD4003 newer part recommended for a new design. You can saves the current data displayed in the chart in a tab delimited spreadsheet. Raw ADC Data is time domain in Codes, FFT or Decimated is in dB. For additional details you view the UG.

    Best regards,

    Lloben

  • 0
    •  Analog Employees 
    on Aug 2, 2018 3:44 PM over 2 years ago
    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