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TMS320F28379D: F28379D Delfino Experimenter Kit

Dany Bourget
Intellectual 350 points
Part Number: TMS320F28379D
Other Parts Discussed in Thread: OPA625

I had a discussion with Errol from TI a few weeks ago, but now I have trouble to get an answer to my questions

see previous post:

I have a problem with the ADC of the F28379D Delfino Experimenter Kit. For some reason we often see multiple samples with the same value. Did someone experience the same problem in the past?

  • 0
    TI__Guru 60865 points
    Hi Dany,

    What are you using to source in the signal for this channel? (I think the issue you are seeing is probably not caused by inadequate input op-amp bandwidth, the subject of the other post, but it is worth looking at)

    Are you also sampling other channels while getting this distorted waveform, or is this the only channel being converted?

    What is the sample rate of this channel?

    Which ControlCard revision do you have? I think R1.1a has some issues with reference circuitry that could cause something like this.

    Have you measured the reference voltage on the pin? Is this as expected at least from a DC perspective? Is the VDDA/VDDIO voltage near 3.3V as expected?
  • 0 in reply to Devin Cottier
    Intellectual 350 points
    Hi Devin,

    Please find below the answers to your questions:

    - The signal source is a waveform generator Agilent 33220A.

    - We tried different sampling combinations with the same result.

    - The sample rate is at 10KHz (we also tried different sample rates and different sample windows with the same result).

    - We have the R1.3.

    - When whe measured the voltage reference, we see a flat line wich is ok (all the ADC values are the same).

    We also tried to simplify the ADC front-end by using only a voltage follower amplifier (OPA625) with Rflt and Cflt with the same result.

    Regards

    Dany
  • 0 in reply to Dany Bourget
    TI__Guru 60865 points
    The discussion continues here: e2e.ti.com/.../567681