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How precise MTBF calculation is?

Mr tester
Prodigy 50 points

I use TPA6211 in MSOP audio amplifiers powered at 5.5V to test small motors( 10 ohm) ,

 The amplifiers are getting really hot , TJ is getting to 120C while dissipating ~ 0.75 watt

From Reliability Data & Reliability Estimator Results

http://focus.ti.com/quality/docs/singlesearchresults.tsp?templateId=5909&navigationId=11213&mtbfType=true&searchType=orderableOption&partialSearch=false&orderablePartNumber=TPA6211A1DRB

I should expect a 23 millions hours MTFB , real operation show less than 5000 hours , I would like to know why I got so bad failure rate??

Thanks.

 

  • 0
    TI__Guru**** 189401 points

    Mr Tester,

    How are you measuring the junction temperature?

    What is your failure rate?

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 50 points

    Hello Mr Dapkus,

       TC is around 110C , I added 10C  to get 120C TJ . Average dissipation per amplifier is ~0.75 watt

       The real question is for a given TJ operating temperature , lets say 120C is the MTBF  equation

        that TI  supply works? The FIT is the same a bunch of amplifier 6203, 6205, 6211... ??

        What happen with amplifier life at VCC = 5.5V

        Failure rate : 1 failure per ~month on a 10 amplifier boards so about a failure for 6500 hours

        This is far far away from what the MTBF equation give me. Why??

     

    Thanks for your support.

       

     

      

     

     

     

  • 0 in reply to Mr tester
    TI__Guru**** 189401 points

    Mr Tester,

    Are you saying you had one failure out of 10, or ?

    I suspect the reason the FIT data is the same for all those amplifiers is they are all made in the same IC fabrication process, using the same design rules, so the FITs are the same.

    Since your request is pretty specific, I think it would be best if you got in contact with the local TI Sales Office in Montreal and asked them for help. Their number is 613-271-3200.

    -d2