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PTN78060W: Thermal resistance information

Ryo Akashi
Expert 8940 points
Part Number: PTN78060W

Hello experts,

My customer considers to use PTN78060W.
To check whether PTN78060W can be used in their system, other thermal information (e.g. RθJA, ψJT) is needed.
On datasheet, there is only Ta information.
Do you have any information about this? Or which information should we refer?
Also, when evaluating the thermal condition, which point should we measure?
Thanks and best regards,
Ryo Akashi
  • 0
    TI__Mastermind 18940 points

    Hello Akashi,

    I think it is best to use the temperature derating vs output current curves. There are many curves in the datasheet and this is real data.
    These curves specify the output current for the application condition (ambient temperature, input voltage, output voltage).

    Let us know if this makes sense to the customer.

    Cheers,
    Denislav

  • 0 in reply to Denislav Petkov
    TI__Expert 8940 points

    Hello Denislav,

    Thank you for your reply.
    Unfortunately, my customer said it is difficult to judge from only temp derating vs current curve on datasheet.
    If you have these information ; θjc, Tj or limit of surface temperature of parts,
    could you share us?
    Thanks and best  regards,
    Ryo Akashi
  • 0 in reply to Ryo Akashi
    TI__Mastermind 18940 points

    Hello Akashi-san,

    I strongly believe that the curves in the datasheet are more meaningful than Theta JA spec.

    There are many components on the board. Looking at Theta numbers assumes the hottest component is the IC. I don't know if this is the case or not.

    Usually the derating curves will take into account all of the components on the module so it is actually more meaningful and more useful.

    I will still request from the team if we have specific IC ThetaJA numbers. I hope to have a reply for you early next week.

    Cheers,

    Denislav

  • 0 in reply to Ryo Akashi
    TI__Expert 8130 points

    Hi Ryo,

    By referencing to the data shown in the figures, a safe operation θjA = 35°C/W

    Regards,
    Alejandro

  • 0 in reply to Denislav Petkov
    TI__Expert 8940 points

    Hello Denislav,

    Thank you for your reply and loop your team.
    I got comment from Alejandro.
    Thanks and best  regards,
    Ryo Akashi
  • 0 in reply to iAlejandro
    TI__Expert 8940 points

    Hello Alejandro,

    Thank you for your post about θjA info.
    I got request from customer.
    My customer wants to know how does TI decide temperature derating.
    If possible, could you share the detail? 
    Also, if possible, could you share the measurement condition (environment, distance from board)?
    Thanks and best regards,
    Ryo Akashi
  • 0 in reply to Ryo Akashi
    TI__Expert 8130 points

    Hi Ryo,

    We determine SOA by the following:

    • We identify the key thermal components of the device (ex. Power FETs, Inductor, etc.)
    • The device is placed on a test board inside an SOA Chamber (this device is placed on a 100 mm x 100 mm test board.)
    • Thermal measurements are taken with infrared camera and/or thermocouples ran at different operating conditions (several representative airflow)
    • Ta_max curves must be calculated for each component and the combined curves set the SOA curve.
    • θjA is calculated based off the Tj of the hottest key component.

    (For future reference, the measurement conditions are indicated in footnotes below the figures. I've attached image below)

  • 0 in reply to iAlejandro
    TI__Expert 8940 points

    Hello expert,

    Thank you for your reply.
    I got question from customer.
    You mentioned 
    "Thermal measurements are taken with infrared camera and/or thermocouples ran at different operating conditions (several representative airflow)"
    "θjA is calculated based off the Tj of the hottest key component."
    It means you can find which part is the hottest on this device by infraed camera or themocouplers. Is it correct?
    If so, could you tell me which part is the hottest on PTN78060W?
    Thanks and best regards,
    Ryo Akashi
  • 0 in reply to Ryo Akashi
    TI__Expert 8130 points

    Hi Ryo,

    The hottest component on PTN78060W is shown on the image below (free wheel body diode).

    Regards,
    Alejandro