LP3876ES-ADJSLASHNOPB datasheet(12/19 Pages) TI

12 / 19 page

LP3876-ADJ

SNVS245C – SEPTEMBER 2003 – REVISED APRIL 2013

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In this equation,

θCH is the thermal resistance from the case to the surface of the heat sink and θJC is the thermal

resistance from the junction to the surface of the case.

θJC is about 3°C/W for a TO-220 package. The value for

θCH depends on method of attachment, insulator, etc. θCH varies between 1.5°C/W to 2.5°C/W. If the exact value

is unknown, 2°C/W can be assumed.

HEATSINKING DDPAK/DDPAK/TO-263 PACKAGE

The DDPAK/DDPAK/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 22 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 22.

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 PCB is 32°C/W.

Figure 23 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 23. Maximum power dissipation vs ambient temperature for DDPAK/TO-263 package

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