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ADS7038Q1EVM-PDK: Signal appearing on other channels

Ryan Chan
Prodigy 20 points
Part Number: ADS7038Q1EVM-PDK
Other Parts Discussed in Thread: ADS7038,

Hi,

I am currently trying to use the ADS7038 on the ADS7038Q1EVM-PDK evaluation module to read signals using the Auto Sequence Mode.

When I plugged a signal generator outputting a sine wave into AIN0 (red), the signal ended up appearing on the subsequent AIN channels:

(red = AIN0, green = AIN1, yellow = AIN2, purple = AIN3, grey = AIN4, light blue = AIN5, black = AIN6, blue = AIN7)

However, when I plugged the signal generator into the last channel, AIN7 (blue), the signal did not appear on the subsequent AIN channels:

(red = AIN0, green = AIN1, yellow = AIN2, purple = AIN3, grey = AIN4, light blue = AIN5, black = AIN6, blue = AIN7)

I was wondering what might be causing this issue? In case it is helpful, here is the code I used:

Any help would be greatly appreciated, thank you!

  • +1
    TI__Mastermind 24940 points

    Hello,

    To make sure I understand correctly, you are using the hardware for the ADS7038 EVM, but not using the GUI and communications card is comes with and instead are using your own host device and code to communicate with the device. Is this correct? 

    EVMs are not intended to be used in systems or final products as is, they are not designed to support this functionality. 

    You should also look at the schematic at the end of the user's guide for the EVM, this will help you a lot. 

    From the graphs you shared, it looks as you are leaving the remaining channels unconnected, or AKA floating. This allows for other signals to couple into the floating channels. I suggest connecting the unused channels to ground. 
    Channel works differently because, if you look at the schematic, it was designed to be used as a digital output. 

    Regards

    Cynthia