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ADS131A02: Internal Reference is unstable at ESD/EFT test

Part Number: ADS131A02
Other Parts Discussed in Thread: REF5040

Hi all,

My customer designed his product using ADS131A02.

However, when he tried EMC test such as ESD/EFT, output data was abnormal.

He checked each pins at this condition and he noticed that internal reference was unstable around 1V~3V whereas nominal value is 4V.

He assumes abnormal output value was caused by unstable condition of the internal reference.


  1. Is there any possibility that internal reference become unstable at ESD/EFT test?
    Do you have any idea what causes this phenomena?
  2. Could you please review customer's schematic from this TI internal link?

Best regards,
Shota Mago

  • Hello Mago-san,

    Thank you for your post.

    Without knowing the details of the ESD/EFT testing, it sounds likely that the device is entering an unknown state which is compromising performance. Is the customer still able to communicate with the interface? Does a reset restore device performance?


  • Hi Ryan-san,

    Thanks for your quick reply!

    I talked with the customer today and got additional information.

    He tested IEC61000-4-2 Level 4 and IEC61000-4-4 Level 4.

    After noise test and internal reference becomes unstable(fluctuate between 1V~3V slowly), the device can be back to normal operation by H/W reset and it's possible to communicate with the interface. So the device is not broken.

    He uses ADS131A02 for multiple different product and all of them show same issue at ESD/EFT test.

    Though he added decoupling capacitor on RESET pin and optimized trace of RESET, the issue still exists.

    Have you ever heard this kind of issue not only for ADS131x but also other ADC?

    I'm suggesting to try with external reference such as REF5040. Is there any other solution to solve this?

    Best regards,

    Shota Mago

  • Hello Mago-san,

    We are discussing how to determine the root cause, but it's difficult to know which pin(s) are being affected by the ESD/EFT pulses, causing the reference voltage to wander. Does the customer have any sort of protection circuitry on the inputs or supply pins? It is important to clamp the voltage and limit the current on these pins to within the ranges listed in the Absolute Maximum Ratings table.


  • Hi Ryan-san


    Thank you for discussing this issue.

    I will ask the customer to double check if they have enough protection circuitry.


    One possible cause is Reset pin.

    Originally, the customer placed trace of Reset pin at inner layer.

    At that condition, this issue was occurred even if lower level EFT test like Level 2 or Level 3.

    When they changed trace from inner layer to top layer, this issue was not occurred at Level 2 and Level 3. But it still exists in case of Level 4.

    Although they added capacitor on Reset pin, it doesn't improve sufficiently.

    Best regards,

    Shota Mago

  • Hello Mago-san,

    I'm not sure why the RESET pin would have this effect. 

    It would be a good idea to check if TVS diodes are used on the ADC supplies. Most likely, the transient voltage is affecting the reference through some internal IC path.


  • Hi Ryan-san,


    I will ask the customer to check protection circuit.

    Thank you so much for your support as always!

    Best regards,

    Shota Mago