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TMS320F28035: The ADC module is damaged during lightning surge tests

Rayna Wang
Expert 3680 points

Part Number: TMS320F28035

Hi Expert,

My customer just meets an issue after lightning surge tests, that 

  • the software could download to chip with emulator.
  • all ADC channels sample value is 4096, even the ADC pin connect with pull down resistance, and the issue has happened twice.
  • the ADC channels mainly simple input voltage, inductor current, bus voltage of H bridge PFC.
  • when connect a 2ohm resistance between digital ground and analog ground, the issue could be avoided. But in normal condition, such as with 50% load, the chip is reset.

Our confusions are,

  1. what kind of factors could only damage the ADC module, but not the whole chip?
  2. what do you think of the debug method that increasing the resistance between digital and analog ground?

Customer hopes to find some opinions to debug with this issue, could you help with this? Thanks!

Best Regards

Rayna

  • 0
    TI__Guru 62975 points

    Rayna Wang said:
    what kind of factors could only damage the ADC module, but not the whole chip?

    We are not aware of any specific design weakness that may lead to such a state when the device is maintained within its Recommended Operating Conditions.

    Rayna Wang said:
    what do you think of the debug method that increasing the resistance between digital and analog ground?

    How are the digital and analog grounds normally treated in this design? My personal intuition is that the best configuration for noise immunity from a surge would be a single, continuous ground plane shared by both the digital and analog grounds.

    Rayna Wang said:
    But in normal condition, such as with 50% load, the chip is reset.

    Can you elaborate on what is initiating the reset? Does the ADC recover after device reset? Is the ADC able to recover through a software reset of the module?

  • 0 in reply to tlee
    TI__Expert 3680 points

    Hi Tommy,

    Customer find the reason that the lightning voltage affect VDDA.

    Thanks!

    Rayna