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INA199: INA199A1DCKR circuit discussion

TT_Chin
Expert 2025 points
Part Number: INA199

Hi ,

I design INA199A1DCKR to monitor the current as attached circuit.

When I connect pin 6 output from INA199A1DCKR to MCU ADC input, then MCU was damaged.

Could you please help us to review the circuit as attached to see if any issue of the circuit for the design?

Attached is the waveform of pin6 output from  INA199A1DCKR basen on different load.

Thank you for your help!

Sincerely,

Chin

INA199A1DCKR_test circuit_output waveform.docx

  • 0
    TI__Mastermind 26335 points

    Hello Chin,

    Thanks for considering to use Texas Instruments.  From your schematic, I see the INA199 is supplied with 3.3V and has a common mode of 13.4V.  Both of these are within the specifications of the INA199 device. As for the load of 1.8A, I expect an output of 1.8V.  This is well under 3.3V.  Additionally, when the INA199 is powered on it should never exceed the device supply of 3.3V.  So under normal operation, the INA199 output should not be destroying your ADC.  Perhaps something weird is happening at startup.

    Can you remove your MCU or cut the trace between the INA199 and the MCU and then monitor your INA199 output with an oscilloscope at startup?  This will let us now whether we have some transient spike that occurs when your system is powered on.

    As for your MCU, how did you determine it was damaged? Does your MCU part not power on, not provide an accurate reading, or exhibit extremely inconsistent data?

  • 0 in reply to Patrick Simmons
    Expert 2025 points

    Hi Patrick,

    Thanks for your answer.

    For the MCU damaged issue, it cannot be power on again and the temperature of IC is very hot. It seems abnormal temperature of MCU IC.

    I just want to confirm if any mistake of the relevant circuit and components of INA199A1 as I attached. But according to your review,the circuit is okay.

    I will further analyze the damaged MCU.

    By the way, Is there any power sequency between V+ (Pin3 ) and IN+(Pin4)/IN-(Pin5)?

    Thank you for your help!

    Sincerely,

    Chin

  • 0 in reply to TT_Chin
    TI__Mastermind 26335 points

    Hello Chin,

    I cannot provide too much information on how the internal circuitry powers up.  However, I can say that you may observe unexpected undesired behavior if your common mode is powered up before the supply.  Previously I did a post on a few different conditions here where the supply was not properly powered up and in some cases you can observe an output that is over a few 100 mV and in one case over a volt.  In these conditions I provided just a DC voltage.  With more dynamic inputs you might see other behavior.  So, if you expect some power sequence in which your INA199 does not power up first, I would definitely probe the output with an oscope during power on.  From there you may need to find a way to power your INA199 or MCU sooner.  Alternatively you may need a switch to stop any undesired signal passing from current sensor to the MCU before either is powered up.