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THS4524: Output failure.

Matthieu Junod97
Prodigy 80 points
Part Number: THS4524
Other Parts Discussed in Thread: ADS1174

Hi,

I am carrying out current measurements using Rogowski coils, one high-speed amplifier THS4524, and one ADC ADS1174. 
When installed, the device is working 24/7 without interruption. 

Few devices are now having a similar issue: after months of operation without issue, I can now see that one of the channels is not working anymore (not always the same channel).

From what we were able to recently measure on the field, it seems that one output of the THS4524 drops down to 1/10 of the awaited amplitude. All power supplies and common mode voltages seem to be good.

Turning the device off and then on again resolves the issue. 

What could cause this kind of behavior? Have you already had feedback on those components that could relate to our problem?

Thank you in advance,

Best regards.

  • 0
    TI__Genius 15975 points
    Hi Matthieu,

    I don't think we have ever noticed the output to drop down suddenly on the THS4524 the way you are describing.

    How are you connecting the Rogowski coils to the THS4524 inputs - are they connected to a socketed input, or the coils are hard-tied/soldered to the THS4524 inputs? Also, it would be helpful to get a schematic of your circuit in-order to better understand the issue.

    One theory could be that the device channel goes into power-down mode while making the input current measurement due to an un-expected surge in current. It might be better to record the PD pin as well while this state occurs to make sure the device is not disabled.

    Best Regards,
    Rohit
  • 0 in reply to Rohit Bhat
    Prodigy 80 points

    Hi Rohit,

    Thank you a lot for your answer. 

    A the moment, a socket is linking the Rogowski coils to the THS4524. I have already looked into it when the failure occurs but it doesn't seem like it has any influence on this issue. 

    Here is a part of the schematic:

    I am using the 38-pin package, the schematic above shows only one of the 4 integrated amplifiers. The 4 others line are exactly the same. The 2 inputs on the left (dI_L3_*) are tied directly to the Rogowski coils and the 2 outputs on the right are tied to the ADC's inputs (ADS1174).

    I didn't think to check the value of the PD pin during a failure. On our schematic, it is tied to the +Vcc but through a 1k resistor. I will check the value next time the failure occurs.

    Best regards.

    Matthieu

  • 0 in reply to Matthieu Junod97
    TI__Genius 15975 points
    Hi Matthieu,

    The THS4524 schematic looks good.

    The only additional component I would recommend adding is a 0.22uF cap from the power down pin to gnd. This cap prevents any fluctuation on the power-down pin due to supply current surge. Other-wise, the schematic should not have any issues related to reduced output swing.

    Best Regards,
    Rohit