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EVAL-AD7124-8 test drive & non-linear response

Question asked by dan.closson on Jun 26, 2018
Latest reply on Jul 11, 2018 by JellenieR

Hi AD Support Community!

 

I've recently acquired an EVAL-AD7124-8 evaluation board which I've connected to an SPI interface on an STM32F4-discovery board. Using the default register values I've tried connecting a lab power supply across channels 0 & 1 and vary the voltage in 5mV increment to see the response. I've discovered that the ADC response is not linear and contains very periodic jumps in the output response?? I've attached a chart that shows the raw ADC counts when varying the input from 1.74V to 1.65V in 5mV decrements.

 

I've tried connecting to other channels on the eval board but I'm getting the same non-linear behavior on other channels. Is there a configuration item that is required that I'm missing? The magnitude of the non-linearity will result in too much error in our application.

 

Help me AD support community, you're my only hope

 

Thanks,

Dan C.

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