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LM2767: Damage was found during the test, with input but no output

Timsen
Expert 1660 points
Part Number: LM2767

Dear all：

        I used LM2767, input 3.2v voltage, output 6.4v power supply for other chips.Now more than 1000 pieces have been produced. During the test, it was found that 15 pieces were damaged, with input voltage but no output.Then change new LM2767 can work normally.The following is my schematic diagram, bit number IC204 is LM2767

       Please help to analyze what causes the damage?Does the fourth pin input of LM2767 chip need capacitance?I used the oscilloscope to see the peak voltage of 5.85v at the input voltage of the 4th pin at the moment of starting up

  • 0
    TI__Mastermind 21720 points

    Hi Timsen,

    Thanks for reaching out with your question and for using the LM2767.

    I would suggest adding a capacitor to the V+ (pin 4). This will help smooth out any transient voltage on the pin. Not that if you are seeing 5.85V on the pin the absolute maximum voltage specification of pin 4 is being violated and can be causing damage. Adding 0.1uF should be enough capacitance.

    -Garrett

  • 0 in reply to Garrett Roecker
    Expert 1660 points

    Dear Garrett:

           I tested 15 pieces were damaged. What may be the reason for the damage?

    Thank you!

  • 0 in reply to Timsen
    TI__Mastermind 21720 points

    Timsen,

    It was mentioned that during start-up the V+ pin is seeing 5.85V. The absolute maximum voltage rating of the pin is 5.8V. If the voltage is higher than the absolute maximum voltage rating it is possible for the device to be damaged.

    Thanks,

    Garrett

  • 0 in reply to Garrett Roecker
    Expert 1660 points

    Hi Garrett:

           The maximum voltage that lm2767 can withstand is 5.8v. The maximum burr voltage that I captured with oscilloscope is not 5.85v, but 5.68v

           So, What else caused the damage of LM2767?

  • 0 in reply to Timsen
    TI__Mastermind 21720 points

    hi Timsen,

    Thanks for sending the waveform. I see that the input voltage only reaches about 5.68V but I think the probe capacitance might be reducing the peak voltage that is seen on the pin. When the pin is not probed it is possible for the voltage to be higher than 5.8V. Has it been possible to do any testing with a capacitor connected to close to the pin? A ceramic capacitor or about 0.1uF should help out.

    Thanks,

    Garrett