Datasheet

LM2940-N, LM2940C
SNVS769H –MAY 2004–REVISED MARCH 2007 www.ti.com
HEATSINKING SOT-223 PACKAGE PARTS
The SOT-223 (“MP”) packages use a copper plane on the PCB and the PCB itself as a heatsink. To optimize the
heat sinking ability of the plane and PCB, solder the tab of the package to the plane.
Figure 12 and Figure 13 show the information for the SOT-223 package. Figure 13 assumes a θ
(JA)
of 74°C/W
for 1 square inch of 1 ounce copper and 51°C/W for 1 square inch of 2 ounce copper, with a maximum ambient
temperature (T
A
) of 85°C and a maximum junction temperature (T
J
) of 125°C.
For techniques for improving the thermal resistance and power dissipation for the SOT-223 package, please
refer to Application Note AN-1028.
Figure 12. θ
(JA)
vs. Copper (2 ounce) Area for the SOT-223 Package
Figure 13. Maximum Power Dissipation vs. T
A
for the SOT-223 Package
HEATSINKING LLP PACKAGE PARTS
The value of θ
JA
for the LLP package is specifically dependent on PCB trace area, trace material, and the
number of layers and thermal vias. It is recommended that a minimum of 6 thermal vias be placed under the
center pad to improve thermal performance.
For techniques for improving the thermal resistance and power dissipation for the LLP package, please refer to
Application Note AN-1187.
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