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ADC102S051: Channel 2 accuracy issues

Robert Rose1
Prodigy 10 points

Part Number: ADC102S051

We are having an issue such that the SPI data coming back from the A/D is incorrect when I choose channel. 2.   My SPI bus has 16 clocks.   The clock frequency is 3MHz, the input data is steady DC levels.  I'm clicking data to the A/D on te negative edge.  I'm looking at the data coming back on and oscilloscope.   The data is present but incorrect.   If I modify the code to read only channel one, it appears to work perfectly.    This is my only spi operation to this component.   I'm not aware of any other setup that I have to do.  As a test, I'm sending data repetitively to this channel only.   I'm not using channel one at this time.

Any ideas.

  • 0
    TI__Mastermind 25070 points

    Hello,

    First, I would like to share that the device support clock frequencies from 3.2Mhz to 8Mhz. You are currently operating the device outside the operating range. Try to increase the clock frequency to 3.2MHz.

    From here, if the problem persists.

    Would you please share the oscilloscope screen shots, including the digital communications signals? This helps to confirm timing and voltage levels

    If I understand correctly, you can get correct data from any channel if sampling it individually, meaning that CS is changed states in between samples.

    It is when you hold CS low to sample channels continuously that you read incorrect data.

    Is this correct?

    If so, I suggest making sure that the oscilloscope images match, in particular the SDI data as this controls the channel selection

    Regards

    Cynthia