LP38513 Datasheet, PDF (12/14 Pages) National Semiconductor (TI) – 3A Fast Response Ultra Low Dropout Linear Regulator

Figure 4 shows the maximum allowable power dissipation for
TO-263 packages for different ambient temperatures, assum-
ing θ_JA is 35°C/W and the maximum junction temperature is
125°C.
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FIGURE 3. θ_JA vs Copper (1 Ounce) Area for the TO-263
package
As shown in the figure, increasing the copper area beyond 1
square inch produces very little improvement. The minimum
value for θ_JA for the TO-263 package mounted to a PCB is
32°C/W.
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FIGURE 4. Maximum Power Dissipation vs Ambient
Temperature for the TO-263 Package
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