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LM76002: New Thermal Metrics

Brian Wang0928
Genius 12510 points
Part Number: LM76002

There is an article of the SBVA025 to talk about the New thermal Metrics. It suggests to using new thermal metric, JB to calculate the junction temp of device.

However, in the Webench tool it still using old thermal parameter. we're confusing how to calculate Tj correctly?

 

  • 0
    TI__Mastermind 18575 points

    Hi Brian

    1.The  θJA :

    In real world, θJA cannot be determined only by the IC. It depends greatly on the application board. Every different PCB has a different θJA value.  The value given by datasheet is applied under JEDEC standard and is not usable for calculating the Tj on your real PCB.

    However, In some datasheets, we give the value θJA_effective. Which is the real θJA value based on the EVM_PCB, Normally the Webench tool use this value. And customer can use this value as a starting point.

    The Figure 86 in datasheet gives the RθJA values vs different PCB cooper area. Which is useful for customer to estimate the Tj before making a real PCB board.

    2. The consideration for  recommending  ΨJB and ΨJT in the publication "

    When you have already built a PCB. It would be more easy and accurate to get the TB or TC, and calculate Tj using the equation TJ = TB + ΨJB*PD or TJ = TC + ΨJC*PD

    Thanks and best regards.