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ADS127L11: ADC damage issue

Cherry Zhou
Mastermind 22235 points
Part Number: ADS127L11

Hi Team,

The customer use the ADS127L11(an ADC chip), to interface the analogue output of the Hall magnetic field sensor.

They have tried to separate the sensor from the ADC by 1.5 meters and there is nothing wrong. The ADC was placed together with the magnetic field sensor at this time, but during the test it was found that the ADC could be damaged as the magnetic field increases. When the magnet is close to the ADC, the timing of the ADC has an impact and as getting closer, it would be damaged.

When the ADC is replaced and placed in a 10,000 Gaussian magnetic field, the ADC will smoke. But none of the other components are affected.

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Mastermind 40990 points

    Hi Cherry,

    I will need to do some tests, but this may take several days before I have some magnets available.

    Can you provide a schematic of all circuitry surrounding the ADS127L11?  Are there any switching power supplies on the same board as the ADS127L11?  I am concerned that one of the voltage supplies to the ADS127L11 is going out of regulation and exceeding the ABS maximum specifications of the ADS127L11.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    TI__Mastermind 40990 points

    Hello Cherry,

    I received the magnets today and did some testing on the ADS127L11EVM board.  There is no sensitivity to a static magnetic field.  However, if I move the magnet quickly up and down above the ADC plus Amplifier, I can induce small voltages, which is expected.  This is due to small loops on the board due to layout of the resistor feedback network around the input amplifier.  The below plot shows a peak to peak voltage of about 1.2mV.

    If the magnetic field was changing at a much higher frequency, then the voltage would go up.  Depending on any unintended loops for the magnetic field to couple into and the frequency of the field, this voltage could go much higher, and in theory, could get high enough to damage the device.

    However, I think it is more likely that a switching power supply is becoming unstable due to the large magnetic field causing the inductor/transformer core to saturate, but this assumes that there is a switching power supply on the ADC board that is exposed to the magnetic field.

    If you have more details on the source of the magnetic field, please let me know.  If you can provide a schematic for the ADC board, that would also be helpful.

    Regards,
    Keith