LP38511

SNOSAU6E – NOVEMBER 2007 – REVISED APRIL 2013

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HEATSINKING DDPAK/TO-263 PACKAGE

The DDPAK/TO-263 and the PFM packages use the copper plane on the PCB as a heatsink. The tab, or DAP,

of these packages are soldered to the copper plane for heat sinking. Figure 25 shows a curve for the

θJA of

DDPAK/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 25.

θJA vs Copper (1 Ounce) Area for DDPAK/TO-263 package

As shown in the figure, increasing the copper area beyond 1 square inch produces very little improvement. The

minimum value for

θJA for the DDPAK/TO-263 package mounted to a two-layer PCB is 32°C/W.

Figure 26 shows the maximum allowable power dissipation for DDPAK/TO-263 packages for different ambient

temperatures, assuming

θJA is 35°C/W and the maximum junction temperature is 125°C.

Figure 26. Maximum Power Dissipation vs Ambient Temperature for DDPAK/TO-263 Package

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