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lm25069 operating rating values of temperature too low

Kamal Najmi
Expert 3295 points
Other Parts Discussed in Thread: LM25069

hi my customer B is asking about the operating ratings on page 3 of the datasheet.

They mentions up to 85 Deg TJ but the part has a TJ of 150DEGREE.

is there a typo?

 

REGARDS,

KAMAL

 

  • 0
    TI__Genius 12380 points

    Hi Kamal,

    Note that the original National datasheet had the same 85C information:

    We are digging into this to see if this is a typo. Because it is a formerly National device, it will take some time to find and analyze the original char data.

     

    The datasheet includes curves of several parameters up to 125C (Figures 10-20). These curves indicate typical values which look ok and would not affect the device's ability to operate at that temperature. But because they are typical values, we must find the char data to see if the EC table values are taken at 85C or 125C.

     

    Thanks!

    Alex

  • 0 in reply to Alex Triano
    TI__Genius 12380 points
    UPDATE

    Hi Kamal,

    We found the char data and everything was taken at 127C. Thus we will be updating the datasheet to reflect 125C in its next rev.

    Thanks!
    Alex
  • 0 in reply to Alex Triano
    TI__Expert 6776 points
    Hi Alex,

    did we ever update the datasheet?
    The same customer as in the original post wants to use the device and they need 125C.

    Do we have a document that states the temperature range?

    Thanks!
  • 0 in reply to franziskus
    TI__Expert 5940 points
    The DS is at a 2013 rev. It hasn't been updated. I see the notation of characterization data being taken at 127C for the DS parameters by Alex. Given that he has reviewed the data operating temp of 125C. It would not be recommended to operate the FET at 125C however as it will significantly de-rate its SOA. This DS will be updated accordingly but isn't on an immediate update schedule.

    Brian
  • 0 in reply to Brian Daugherty
    TI__Expert 6776 points

    Hi Brian,

    my customer needs support for 125C. As I understand, the LM25069 can support 125C because the characterization was actually done at 127C.
    Even though the datasheet says "Operating Ratings Junction Temp. Range: -40C to +85C", it should actually say -40C to +125C.

    Can you confirm my understanding is correct?

    As the FET is external I would inform my customer that they need to check if it supports 125C.
    Do you have any other concerns besides the FET?

    Thanks! Appreciate your support!

  • 0 in reply to franziskus
    TI__Expert 6776 points

    Hi Brian,

    can you confirm my understanding above is correct?

    Thanks

  • 0 in reply to franziskus
    TI__Expert 5940 points
    Yes, that is correct based on Alex's review of the characterization data and the DS 'nominal' characterization plots. Regarding the FET, if you operate it at 125C and then need to survive a fault with restart, or even just considering normal power up stress, the SOA parameters in the FET's DS need to be derated by (Tj rating - 125C) / (Tjrating - 25C). So you can see the SOA window is much smaller and the risk of FET failure is much higher due to SOA violation. Also consider that if the IC = 125C, the FET, being a heat source, will be higher temp.

    Brian