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LMZ23605: LMZ23605 / Junction-to-case (Bottom) thermal resistance

Part Number: LMZ23605
Other Parts Discussed in Thread: LMZM33603

Hi,

I know that LMZ23605 has Junction-to-case (Top) thermal resistance, then do you have also Junction-to-case (Bottom)? If you don't have, do you estimate if Junction-to-case (Bottom) is lower than Top?

Best Regards,

Satoshi / Japan Dsity

  • Hi Satoshi,
    I am currently looking at this and will get back to you.
    Regards,
    Jimmy
  • Hi Satoshi,

    It's hard to say whether junction to case (bottom) would be lower than top.  TI has started to characterize the junction-to-top and junction-to-bottom characterization parameter with a different parameter(phi).

    It is my understanding that power is dissipated into the PCB through the exposed pad so we would expect more thermal rise on the board. This would result in a higher junction-to-bottom characterization parameter.  A good example of this is the LMZM33603 where the majority of heat is dissipated through the PCB and the datasheet specs it as such:

    Because of this, I think the junction-to-board characterization parameter will be higher than junction-to-top characterization parameter for the LMZ23605. For more information on this new parameter please take a look at this Thermal Metrics application note. 

    Regards,

    Jimmy