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SN74LVC244A: Thermal Information for package TSSPO PN: SN74LVC244APWRG4

6230158
Prodigy 40 points
Part Number: SN74LVC244A

Hi, 

I wanted to know about the Thermal resistance of PN: 

SN74LVC244APWRG4

Specifically interested in the thermal resistance Theta JC Bottom value which is not provided for this specific part number for the TSSOP package.

Thanks!

  • 0
    Guru 277400 points

    The TSSOP package does not have an exposed thermal pad at the bottom and does not touch the PCB, so specifying RθJC(bot) does not make sense.

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points

    Hi, 

    I guess my question is coming more from the standpoint of potentially using some type of thermal epoxy to bond the bottom of the case to the board instead of leaving an air gap. This would allow some heat to go through this larger surface area path instead of having to go only through the leads to the junction. 

    If I were to use a thermal epoxy, would it be fair to say that the temp rise from the bottom f he case to the junction would be smaller than what is given for the junction to the top? Any way to approximate what it would be, or would this be somewhat negligible?

    Thanks!

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points

    Hi, 

    I guess my question is coming more from the standpoint of potentially using some type of thermal epoxy to bond the bottom of the case to the board instead of leaving an air gap. This would allow some heat to go through this larger surface area path instead of having to go only through the leads to the junction. 

    If I were to use a thermal epoxy, would it be fair to say that the temp rise from the bottom f he case to the junction would be smaller than what is given for the junction to the top? Any way to approximate what it would be, or would this be somewhat negligible?

    Thanks

  • 0 in reply to 6230158
    TI__Mastermind 24805 points

    Hello, 

    Since there is no thermally conducting pad on the bottom of the device, adding any epoxy from the plastic bottom of the package to the board is not going to help with thermal transfer because the vast majority of the thermal conductivity is going to happen through the leads.

    I honestly would not recommend adding an epoxy to the bottom of the chip, as I don't believe that it would provide any benefit. Its safe to assume any change would be negligible. 

    The device is unlikely to heat up that much anyway as its not a power chip or something that is conducting a lot of current, so in general thermals on a simple logic buffer device is not going to be a concern.

    Best,
    Michael