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TLV1117: Difference Package Thermal Resistances

Part Number: TLV1117


Good Day.

The customer was confused with TLV1117 different package thermal resistances. Package DRJ (QFN) has a junction-to-ambient thermal resistance of 38.3 'C/W and package DCY (SOT-223) has a junction-to-ambient thermal resistance of 104.3 'C/W but junction-to-board numbers are 60.5 and 5.7 similarly. So which of the packages is actually better thermally when mounted on a PCB with large copper areas?

Maximum power dissipation would be approximately 1.2 W and he is wondering if he can use the QFN package for a smaller size.

They are currently using the SOT-223 package of this part and it has no problem with 1.2 W dissipation so if QFN is better it could be used. But he is not sure about that when looking at the numbers given in the datasheet.

So if properly designed, can the QFN package dissipate more or less power than SOT-223?

Please advise. Thank you very much.

Best Regards,

Ray Vincent

  • Hi Ray,

    The J to A thermal resistance is the metric that is most commonly utilized, this would mean that the DRJ package has improved thermals.

    The junction to board parameter is under the assumption that all of the thermal energy is being dissipated through the board. Under this assumption, which is an idealized case, the DCY package is more effective, however under all cases, when the other pathways through the case and air are considered, the QFN package performs better than the DCY. They should be able to switch to the new package with good design practice. Additionally with large GND plane and good design the customer can make the package perform even better than the metrics listed on the datasheet as those are defined with a specific Jedec standard in mind.