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INA199: Current monitor gets destroyed on load application

Christopher Chinavare
Prodigy 30 points
Part Number: INA199

Hello,

I have a INA199 current monitor with a 5 mOhm shunt. The INA199 is powered with a 3.3V supply, the reference pin is tied to ground and the shunt has 24V going through it. The output pin is then read by an ADC on a microcontroller.

On the latest revision of a board, I'm having an issue where the INA199 gets destroyed when the load is applied. After seeing this happen with one board, I tried it with a second board and slowly ramped up the 24V supply across the shunt with a 50 ohm resistor on the output. The INA199 was working great and the microcontroller was reading 480mA at 24V as expected. I disconnected the load with the 24V voltage still applied and the contacts must have briefly made a connection again as the INA199 went up in smoke. The power input pin disconnected from the chip and stayed attached to the PCB pad. 

I have this same setup on a previous revision of the board which works fine using that same test procedure and same 24V supply. The only difference between the 2 is that the previous revision used a 5V supply whereas the new, troubled revision uses a 3.3V supply. Any thoughts on what could be causing this? Would the supply voltage being at 3.3V vs 5V make it less robust to transients on the 24V line?

  • 0
    TI__Mastermind 31830 points

    Hi Christopher,

    Do you know which version of INA199 is being used on the board? It is recommended to use B or C instead of A in the application you described. The reason is given in the datasheet:

    Regards, Guang

  • 0 in reply to Guang Zhou
    Prodigy 30 points

    Thank you for the response Guang. I did not see that part in the datasheet until after I started having the issue. That's certainly a possibility though.

    I do not know the revision of the parts I'm currently having the issue with. The Rev A of my design, which is working fine used parts that I ordered and installed from digikey. Rev B of my design, which is having issues, was assembled by a PCB prototype house and it's possible they were using old stock. They source parts from LCSC, but also maintain stock of their own, so I can see how that could happen.

    I did order more of these from digikey last week and they should be here tomorrow. I'll see if I can get a revision of the parts before I install them.

  • 0 in reply to Christopher Chinavare
    TI__Mastermind 31830 points

    Hi Christopher,

    Sounds good, please let us know your findings.

    Regards, Guang

  • 0 in reply to Guang Zhou
    Prodigy 30 points

    Hello again Guang.

    I received my parts today with a Feb 2020 date code, Lot 0027088NFM. I have installed two of them and they both seem to be working as intended. Thank you very much for the help!