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ADS1263: Ferrite Bead on ADS126x AIN pins

MARIO MAINO
Prodigy 70 points
Part Number: ADS1263

Do you notice Ferrite beads can be useful to reduce EMI noise injection from cables connected to the AINx pins or resistors+capacitors are enough as in the datasheet example?

Thank you very much and have a good day!

  • 0
    TI__Mastermind 39811 points

    Hi Mario,

    We see many customers adding ferrite beads on the ADC's analog inputs (in addition to an RC filter) to help reject higher frequency noise. Unfortunately, I do not have any quantitative data to suggest this is a good idea or that the beads really help. The answer to this question would likely depend on a lot of factors, including the frequencies of the noise you are trying to reject, the ADC you choose, any additional filtering, and most certainly the PCB layout. In other words, if ferrite beads help in one system they may not work in another, depending on these factors, so there is no definitive answer to this question.

    The best suggestion I have for you is to add a placeholder for ferrite beads that can be bypassed with a 0 ohm resistor. Then, test the efficacy of the ferrite bead performance and decide if it makes sense to keep them in your system. If you do perform these tests, it would be great if you could share your results on the forum as a data point for other engineers.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 70 points

    Hello and thanks for your answer. I have a problem with the EMI emissions from a servomotor, which at startup (especially at low speed) causes a steady drop in my load cell values (about 0.5-1% in reading values). I tried to use some ferrite on the wires with a little signal enhancement. When I turn off the engine, the values stay fixed on 0.

    During measurement, the voltage between VREF and Ground remains fixed (2.5V).

    I have tried to improve the motor and the servo drive ground, have supplied the MCU with a battery, and have removed any connection between the motor and the MCU board (ModBus and digital controls) without great effects.

    Probably the best solution will be to change the servo motor...

    Best Regards

  • 0 in reply to MARIO MAINO
    TI__Mastermind 39811 points

    Hi Mario,

    Yes, this can be a very tricky issue. One other thing could be to use shielded cabling/wires between the load cell and measurement system. Maybe you have already tried this and it did not help, but I figured I'd mention it since it was not included in the list of things you have already tried in your previous post.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 70 points

    Hello Bryan.

    Load cell cables are shielded (the load cell is already wired and its wire cannot be removed). I linked the wire shield to MCU GND, but someone suggests me to connect it to AINCOM. I think it's unuseful and I'm afraid it can be dangerous for the ADS1263, but I'm not sure.

  • 0 in reply to MARIO MAINO
    TI__Mastermind 39811 points

    Hi Mario,

    I agree, I would not tie the shield to AINCOM. Normally the cable shield is connected to earth ground.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 70 points

    Thanks a lot, Bryan.