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ADS1148: crosstalk issue from other channels

Wu JW
Intellectual 2935 points
Part Number: ADS1148
Other Parts Discussed in Thread: ADS1248

Hi, Team,

My customer found there some crosstalk issue for the ADS1148. When they measure the CH1 for the ADS1148 and no input signal for the CH2~CH4, but there still have the data output for the CH2~CH4 occasionally. We connect the input for the CH2~CH4 to the GND, there still have the data output.

The SCH as in the attachment.ADS1148.pdf

  • 0
    TI__Intellectual 2935 points
    Is there any problem for the SCH? How can we solve this issue? Thanks a lot!
  • 0
    TI__Guru* 97775 points
    JW,


    The isolation from channel to channel on the ADS1248 should be very good and there shouldn't be any signal coming from other channels. Can you provide data from the system? It would be helpful to have the data coming from the ADC, to see where the problem is coming from. For data, it would be helpful to look at these things:

    1. What is the voltage on channel 1? What is the voltage from channels 2-4?
    2. What is the output code from channel 1? What is the output code from channels 2-4?
    3. How often do they see the error in readout from channels 2-4?
    4. What sequence are they reading data? Do they read each channel from 1 to 4 in order? How much time is there between readings?
    5. Have they checked digital communications? Do they use /DRDY as an interrupt read from the device? Do they use an SDATAC at the beginning so that new ADC conversion results do not corrupt other data transactions between the master an the ADS1148.

    I've looked through the schematic and I don't see anything wrong with circuit. However, it will still be helpful to know what they are measuring, how they have their system set up, and what sequence of commands are sent to the device.


    Joseph Wu