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LM2904: part latches when input pulled below ground

Allen Wachter
Expert 6730 points

Part Number: LM2904

Customer is seeing what appears to be LM2904 latching something on and drawing excessive current from the Vcc supply.  Pulling one of the inputs of the op amp below ground briefly which seems to be the trigger for the latching.  In the past, they have seen this (pulling input below ground) cause the output to “phase reverse”, but not latch. 

 

To make things more interesting, he replaced the component with an older date code and the latching did not occur.    So two part question:

 

(1) would pulling the input briefly below ground (~ -1.5V) cause this device to latch?  

(2) is there another dual soic8 part that will not latch?

 

Thanks!

  • 0
    TI__Guru**** 174806 points
    Allen,

    I have not seen that before. The LM2904 passes standard -100mA latch up, which means ICC current should not latch.
    -1.5V is pretty large, does the customer know how much input current is flowing? Also try to get full part number and data code markings.

    For a LM2904 replacement, I would need to know VCC voltage.