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LM25011 damaged during EMC testing

Colin Helliwell
Prodigy 150 points
Other Parts Discussed in Thread: LM25011

We've a design using the LM25011 as the first regulator stage - 24Vdc nominal input, 14V output. The prototype works fine but the LM25011 has failed during EMC Approvals Testing. This was whilst testing for Conducted DC Immunity - 11V of common mode RF applied to the +24V and 0V input lines simultaneously (simulating a radio signal nearby). During this test the regulator circuit failed, ceasing to put out any output voltage. The circuit did not recover. The IC has been replaced and indeed was the faulty component, but on re-test it again died.

The (core of the) circuit was generated by WEBENCH. Would be grateful for any feedback on how/why the IC would be terminally damaged by this test (and possible fixes!)

Thanks
 

  • 0
    Prodigy 10 points

    Hello Colin,

    we have the same problem, the LM25011 has failed during EMC Testing (Conducted DC Immunity), the Lm25011 died. Did you have some feedbacks. We did not find to solve the reason of failure.

    Thanks

    Dietmar

     

  • 0 in reply to Dietmar Berndt
    Intellectual 600 points

    Hi,

    We are starting a new design and we are interesting using this part. From what I found on the forum, ABS input voltage seems to be very critical. Momentary spikes, even very short one will damage the device.

    Does any FAE can answer this question please? How can we design the input voltage of this DC_DC to avoid problem with EMC test (Conducted DC Immunity)???

    Thanks,

    Denis

  • 0 in reply to Denis Alain1
    TI__Genius 11490 points

    Hi Denis,

    We apologize for the delay in reply.

    Will it be possible to show the test setup . Does not have to be very detailed. I am trying to understand if the test in any way violated the specs on the part.

    Regards,

  • 0 in reply to Vijay86929
    Intellectual 600 points

    Hi,

    In fact, if you looked at the beginning of the thread, this thread wasn't started by me, but it seems that 2 different companies experimented what "seems to be" the same problem: damage of the device caused by the same EMC test.

    Since I'm about in the same situation for my new design: 24VDC input, with 12VDC output and I will have to pass the certification also, what do you recommend to avoid problem with the test mentioned: "Conducted DC Immunity"?

    Should I have to add extra capacitor (from what Webench proposed) at the input of the LM25011?

    They are other threads also who mentioned damage of the device caused by some spikes voltages at the input of the device.

    Maybe I'm too alarmist and it's only an isolated case!

    Thanks,
    Denis

  • 0 in reply to Denis Alain1
    Prodigy 150 points
    We did a tweak of the components and subsequently got thru EMC tests without further problems. I'm away at the moment, but will look up and post further info later next week.
  • 0 in reply to Colin Helliwell
    Prodigy 150 points

    We altered the switching frequency to ~100kHz, and also added a common-mode choke to the power input.

     

  • 0 in reply to Colin Helliwell
    Intellectual 600 points

    Hi Colin,

    Many thanks for your comments! We will add a common-mode choke in case of! It could save us time and money!

    Regards, 

    Denis