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UCC12040: UCC12040 thermal test

Rock Shao
Expert 2585 points
Part Number: UCC12040
Other Parts Discussed in Thread: UCC12050

Hi Team,

My customer test the UCC12404 with ISO-EVM, and used 10K to pull high to active the gate driver,
In this state, they found that the upper left corner of the IC thermally rises by 70C when the ambient temperature is 28C with no load and full load of 90mA/3.3V.

Is this status normal? thanks.

You can find the setup in the following pic.
(Excuse me, my customer ask me to delete the product information)

  • 0
    TI__Genius 11570 points

    Hi, Rock,

    I want to confirm your test results: 

    At no load, IC temperature is 28C;  at 90mA load, IC temperature is 70C. 

    The ambient temperature is 20C. 

    Can you confirm it?

    What is the VIN?

    Thanks,
    Sean

  • 0 in reply to Sean Xu
    Expert 2585 points

    Hi Sean,

    In Amb 28C, please see the following test results:

    1. At no load IC temperature is 70C

    2. At 90mA load, IC temperature is 68.1C

    The Vin is 5V.

    Thanks and best regards. 

  • 0 in reply to Rock Shao
    TI__Genius 11570 points

    Hi, Rock,

    Thanks for your clarification. From the layout, it seems that there is not enough copper and vias to heat relief. By the way, how many layers does the board have? Does the temperature reading match with thermalcoupler?

    Regards,

    Sean

  • 0 in reply to Sean Xu
    TI__Genius 13125 points

    Rock

    Also, please ask to remove the 10k pullup and connect EN directly to VINP (5V) just like we show in the EVM User Guide.

    Steve

  • 0 in reply to Steven Mappus1
    TI__Genius 11570 points

    Hi, Rock,

    It is curious to se there are no caps populated on the board. Are they on the bottom side? Do you have the schematic?

    Thanks,

    Sean

  • 0 in reply to Sean Xu
    Expert 2585 points

    Hi, Teams,

    The customer can't provide the schmatic because of the NDA, and they only test dc/dc converter with 2-layer PCB and there is no copper foil on the bottom of the IC.

    Test Conditions
    Vin=5V, Iin=101.62mA, Vo=3.3V, Io=0A, Amb.=115C, used thermocouple to tested.

    The customer tests the IC surface temperature to 144.6C and the PCB temperature to 134.7C when the ambient temperature is 115C. Is there a formula to calculate and confirm that the IC internal die is safe under this condition?

    Excuse me, under what circumstances is the TJ and TA temperature canonical expressions defined in the datasheet?

  • 0 in reply to Rock Shao
    TI__Genius 13125 points

    Rock,

    Even without a schematic provided, the photo you provided does not show any input and output capacitors. Placeholders are shown with no capacitor populated. where are the input and output capacitors populated? Are they populated?

    Secondly, I would suggest to order the UCC12050 EVM which demonstrates the correct PCB design and capacitor placement. The EVM can be used to compare what your customer is seeing. The EVM is available on Digikey here or from TI direct here.

    Regards,

    Steve M

  • 0 in reply to Steven Mappus1
    Expert 2585 points

    Hi Steven,

    Because the schematic and PCB placement is confidential to the customer, I will try to ask them to provide an offline to discuss this question. Could you help to provide your E-mail address? thanks.

    The customer had the EVM and will double-check the thermal with it.

  • 0 in reply to Rock Shao
    TI__Genius 13125 points

    Rock,

    I'm actually less interested in the schematic right now because the schematic may show the input /output capacitors but I still do not see them populated on the PCB picture you have shown and this is more concerning. I'm glad they have the EVM - are they seeing similar temp rise with the EVM?

    Steve

  • 0 in reply to Steven Mappus1
    Expert 2585 points

    Hi Steven

    Thanks for your patient answer.
    I will confirm with the customer whether the current volume product has input/output capacitors configured like EVM. I'll discuss it with you after the customer confirms the EVM.