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OPA564: Thermal issue

Part Number: OPA564

Hi Team,

My customer is using OPA564AIDWP and found thermal issue. When this part is under operation the case temperature is around 90degC, RD would like to know is it helpful if he adds a heat sink(since the thermal pad is under device)? Is there thermal resistance data of DWP package with a heat sink? There is a application note, SLMA002G, that describe the relationship between θJC and via number in figure9, can RD refer to this plot to get θJC value if he follows the thermal via patterns?

Thanks very much.

Best Regards,

Vincent Chen

  • Hello Vincent,

    We have not done any development of an external heatsink solution for the OPA564AIDWP (bottom PowerPAD). We have done a little work on the OPA564AIDWD (top PowerPAD) to test the effect of adding a heatsink and that proved helpful in decreasing the device temperature. We have had at least one OPA564AIDWP customer who attached a custom heatsink to the PC board directly to the underside copper beneath the PowerPAD. Doing this increases the surface area and will allow for the heat to be more effectively radiated. However, there is limited benefit of increased surface area and thermal resistance which can be seen in datasheet Figure 47, Thermal Resistance vs Circuit Board Copper Area.

    In June I requested that a new CAD/CAE symbol be created for the 20-pin HSOIC (DWP) package; one that would optimize the via design for maximum heat conduction. I believe that was added to the website at the time and is now listed CAD file (.bxl) and STEP Model (.stp) listings under the web page Quality and Packaging tab. When I open the STEP file I see the June 2017 date listed. I wouldn't expect this to make a big difference in the device temperature. 

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • Hello Thomas,

    Thanks a lot for the comment, I have proposed customer to add a heatsink under the opposite PCB side but they have mechanical limitation, they are still considering this solution.

    There is an another question, why θJC > θJA ? θJA =θJC +θCA  and θJA  should has larger number.

    Many thanks.

    Vincent 

  • Hi Vincent,

    The OPA564 datasheet isn't very clear about the about the theta designation associations. I found the original thermal characterization report and it provides more useful information:

    The theta-JC (top) is the junction to the case top thermal resistance which is not the primary thermal path. It is the theta-JC (bottom) that is the primary thermal path. The 1.83 deg-C/W is the number that should be used in the junction temperature calculations.

    Regards, Thomas

    Precision Amplifiers Applications Engineering