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LM339: issue with output goes low randomly

Akhil Kalariya
Prodigy 40 points
Part Number: LM339

Tool/software:

We've designed circuit using part number - LM339DRG3.

Circuit is used as basic comparator.

Multiple IC's are present on board with same part number and similar circuit.

Suddenly All IC's output goes low irrespecitve of input signal changes.

After Power restart of 5V supply all works normally again.

Please find below circuit diagram for reference.

  • 0
    TI__Guru**** 152176 points

    Hello Akhil,

    1) Does any input go below (more negative than) -0.3V? ; Probably much below.

    2) Does the pull up voltage for all the outputs drop to 0V?

    3) Does the reference voltage of 160mV (V R72) go suddenly much higher?

    These are the only reasons that come to mind that would match your symptoms.

  • 0 in reply to Ron Michallick
    Prodigy 40 points

    Hello Ron,

    At the time of the issue, I was not able to check the input because the PCB was not accessible without removing power.

    1) Does any input go below (more negative than) -0.3V? ; Probably much below.

    In a single system, we have around 100 sensor inputs, and it is highly unlikely that all of them would suddenly go wrong unless there is a problem with the 5V supply, as per my observation.

    2) Does the pull up voltage for all the outputs drop to 0V?

    Yes, all sensor outputs drop to zero suddenly and never recover, except after a power restart.

    3) Does the reference voltage of 160mV (V R72) go suddenly much higher?

    Not measured at the time of the issue, but there is a voltage divider, and 3.3V is perfect on the supply side, so this is unlikely.

    It seems like something is wrong with the 5V supply to the IC, which is causing this behavior.

  • 0 in reply to Akhil Kalariya
    TI__Guru**** 152176 points

    Akhil,

    Akhil Kalariya said:
    have around 100 sensor inputs, and it is highly unlikely that all of them would suddenly go wrong

    So many more than one LM339 stops working at same time. The 5V supply is the common item.  

    Akhil Kalariya said:
    t seems like something is wrong with the 5V supply to the IC, which is causing this behavior.

    I agree.