Datasheet

LP3853, LP3856
SNVS173G –FEBRUARY 2003–REVISED APRIL 2013 www.ti.com
HEATSINKING TO-263 PACKAGE
The TO-263 package uses the copper plane on the PCB as a heatsink. The tab of these packages are soldered
to the copper plane for heat sinking. Figure 32 shows a curve for the θ
JA
of TO-263 package for different copper
area sizes, using a typical PCB with 1 ounce copper and no solder mask over the copper area for heat sinking.
Figure 32. θ
JA
vs Copper (1 Ounce) Area for 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.
Figure 33 shows the maximum allowable power dissipation for TO-263 packages for different ambient
temperatures, assuming θ
JA
is 35°C/W and the maximum junction temperature is 125°C.
Figure 33. Maximum power dissipation vs ambient temperature for TO-263 package
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