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LM2903-Q1: Destroyed part, hint for root cause?

Part Number: LM2903-Q1

Team,

my customer reported a destroyed LM2903-Q1 on a prototye board. We cannot investigate because the part is destroyed.
I would like to help them to get an idea where to look in their application.

They have done impedance tests with the destroyed part:

pin8 (VCC) to pin4 (GND)     -> 97 Ohm
pin1 (OUT) to pin4 (GND)     -> OL
pin2 (IN-) to pin4 (GND)        -> OL
pin3 (IN+) to pin4 (GND)       -> 43 Ohm
pin8 (VCC) to pin1 (OUT)      -> OL
pin8 (VCC) to pin2 (IN-)         -> OL
pin8 (VCC) to pin3 (IN+)        -> 97 Ohm

Can you confirm that such destruction and the measurements could be caused by overvoltage of VCC on the part?

Thanks!

  • Hi,

    Thanks for your question. As we are currently out for the holidays, we will get back to you as soon as we can the first week of January.

    Regards,
    Jaskaran
  • Hello FRAMziskus ,

    It is difficult to tell from "resistance" measurements due to the wide variation in applied voltage/currents by various DMM's.

    Normally you should see a "diode" across the supply pins in one direction, and a high impedance *if* the applied test voltage is less than the minimum operating voltage (or about 1.2V for the LM339 family). The inputs and output should show a diode in one direction and high impedance in the other direction from ground, and high impedance in both directions from V+ (the LM339 family does not have ESD diodes to V+).

    If you are seeing a solid resistance measurement in both directions, most likely it is a melted junction (short). Typically we would expect "melting" to occur if the voltage is about 45V and the available current is high enough. Voltage just above abs-max can cause soft-failures that may not be immediately noticeable.

    The LM2903/LM339 family is pretty rugged. The inputs can withstand up to 36V even with no supply. What kills these devices is negative voltage - or taking any pin below the GND pin by more than 500mV.

    Pin 3 also looks damaged, though it does show a slight difference in readings depending on polarity (still some functioning junctions).

    I would investigate if the supply voltage is exceeding Abs Max, and if the supply and/or Pin 3 is going negative at some point. Run through a complete power up-down cycle and watch for transients at power-up, operation and power-down (and wait a few seconds until all caps have discharged). Use a scope and monitor all four pins (V+, IN+, IN- and Out).

    Can you provide a schematic and the conditions of the failure?

    Regards,

    Paul Grohe

    Low Power Amplifiers and Comparators (LPAC) Applications

  • In reply to Paul Grohe:

    Hello Paul,

    thanks for this detailed answer. The hint to negative voltage might be an interesting clue for my customer.
    I will come back if needed.

    Thanks!