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OPA551: Heat sinking the DDPAK/TO-263 package

Ian Stedman
Prodigy 30 points
Part Number: OPA551

Hi,

Can someone clarify the correct connection method for the tab on the OPA551 DDPAK package. In section 5, (pin configuration and functions) it states that the tab should connect to the V- supply. In section 9 (power supplies), it states:

The tab of the DDPAK/TO-263 package is electrically connected to the negative supply (V–). However, this connection must not be used to carry current. For best thermal performance, solder the tab directly to the PCB copper area (see the Heat Sinking section).


Currently in our designs, the tab is floating. For a new application, I am looking at using vias to heatsink the tab to the V- (-15V) power plane but if I do this am I causing more problems?

I want to lower the thermal resistance to reduce the thermal resistance as in the new application we need a higher ambient temperature.

Any advice appreciated.

  • 0
    TI__Guru* 93105 points
    Hello Ian,

    The OPA551 DDPAK tab is common to the V- supply pin number 4. And although the tab can have its own floating thermal plane and the OPA551 operation be normal as you have found, it may be convenient to connect the tab to the V- plane and use it as the heatsink. You shouldn't observe much difference in thermal performance if you tie the tab to its own plane, or tie it to V- providing their associated thermal impedances are equal to each other. The concern is if the solder tab via connections made to the V- copper plane can achieve a thermal impedance as low as that achieved by a heat sink plane that doesn't rely on vias for heat transfer.

    Regards, Thomas
    Precision Amplifiers Applications Engineering
  • 0 in reply to Thomas Kuehl
    Prodigy 30 points

    Hello Thomas,

    Thank you for the clarification. I will amend the design to heatsink the tab to the -15V (V-) plane. Based on a simple thermal model, it should lower the junction temperature by 25C, a great result.

    Regards,

    Ian