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LM2576HV: LM2576HV failure after the long duration

Mahendar Reddy
Prodigy 70 points
Part Number: LM2576HV

We are using LM2576HVSX-ADJ/NOPB in one of EV DC-DC converter for auxiliary supply. We have supplied around 5000 No’s to Mahindra Electric. We have not Observed any failures in development Phase and reliability tests but in field we are observing some failure after working for 10days. Specification is as below.

 Input Voltage          36V Dc- 59V Dc

Output Voltage       14.2 VDC

Output Current       350mA

Note: In failure we are Observing first and second Pins getting burn and showing short.

Please find the attached images

  • 0
    TI__Mastermind 32950 points
    Hello Mahendar,

    It appears to me the layout is non ideal. Usually, when the package looks burnt like this, the most likely cause is over voltage. Over voltage can occur, when you have a hot plug of the input voltage to the device. if failure are occurring during a hot plug event, it is likely that the input voltage is overshooting and you will either refrain from such action, or provide external protection like TVS but more important the TVS needs to be placed close to the Device Vin and Gnd. As mentioned on the onset, a poor layout does not help this either.
  • 0 in reply to David Baba
    Prodigy 70 points

    Hi David,

    Please find the attached PCB lay out we have provided TVS diode also. In our actual application Input is Li ion battery pack in Vehicle  Connected through NTC and Diode  and we provided TVS diode SMBJ60A at the input of LM2576HV. Kindly confirm that whether we can you use LM2576HV for 59 V DC Input or not. If we use it at 59V DC is there derating occurs for it. Because We have tested continuous  test  for almost 45 Days at  65 Deg  and -20 Deg temp Thermal Shock cycling test for Main Unit at that time also we have not observed at failures.

    Failures are observing at different following scenarios in vehicle.

    1. Some are getting fail at initial switch ON Condition at Vehicle manufacturers production line.

    2. Some are failing after vehicle running observed 8K Kms, 2k Kms 15K kms.

     

  • 0 in reply to Mahendar Reddy
    TI__Mastermind 32950 points
    Hello Mahendar,

    The device is capable of operating at 59V in without de-rating. the Absolute maximum before potential failure is 63V. I did not see any attachment, but the TVS will need to be placed very closely to the device in order to adequately protect, if this is indeed the failure mechanism? Was the power supply tested for stability? Do you have a actual a BOM? check the saturation current level of the inductor you used, make sure it is higher than the max current limit of the device. Also if you are using an input filter make sure it is well damped.

    Hope this helps?