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INA333: input failures: on INA333 AIDGKT

Benjamin Hoejgaard
Prodigy 20 points
Part Number: INA333

I have seen several failuren on our pressuremeasurement boards, resulting in an - almost short on the positive input terminal.

We are using a Wheatstone bridge as input with an impedance of 1.5kohm. the supply is configured as a single supply +5V.

according to the "normal" datasheet the input should be able to withstand an overvoltage if the current is held under 10mA. 

teh input has a higher input voltage fx. at startup the bridge will limit the current to 3mA -so no problem!!

when i look at Ti homepage: the input at  INA333AIDGKT is only able to withstand a overvoltage at +- 0.1V but at the datasheet it is +- 0.3V

Is it possible that the INA333 AIDGKT has a different input protection circuit?

bg. Benjamin 

  • 0
    TI__Genius 10850 points

    Hi Benjamin,

    Thank you for your post. The INA333 recommended input range extends 0.1V beyond the rails. The +/-0.3V you see is under the absolute maximum ratings. The device is not recommended to operate under these absolute maximum ratings for an extended length of time as it may cause permanent damage to the device.

    -Tamara

  • 0
    Guru 140200 points
    Hi Benjamin,

    limit the input current to 1mA, if you repeat this overvoltage condition for longer periods. The internal clamping diodes to the rails are for ESD protection only, but not as an overvoltage protection for repeated misuse.

    I would mount additional clamping diodes from the bridge outputs to the rails and insert current limiting resistors between the clamped bridge outputs and the inputs of INA333. I use the BAV99 for this sort of clamping. Choose a current limiting resistor of >1k each.

    Kai
  • 0
    TI__Genius 10850 points
    Hi Benjamin,

    I hope we were able to answer your question / resolve the issue. I am going to close this thread now. If you have any more questions regarding this device, feel free to reply to re-open.

    -Tamara Alani
  • 0 in reply to kai klaas69
    Prodigy 20 points
    Hi Kai, Thanks -
    I had my suspicion regarding the input current but couldn’t find any data on that. I'll insert a RC filter in both inputs.