LP38851S-ADJ Datasheet, PDF (18/29 Pages) Texas Instruments – LP38851 800 mA Fast-Response High-Accuracy Adjustable LDO Linear Regulator with Enable and Soft-Start

LP38851
SNVS492C – JUNE 2007 – REVISED APRIL 2013
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Heat-Sinking The SO PowerPad Package
The LP38851MR package has a θ_JA rating of 168°C/W, and a θ_JC rating of 11°C/W. The θ_JA rating of 168°C/W
includes the device DAP soldered to an area of 0.008 square inches (0.09 in x 0.09 in) of 1 ounce copper, with
no airflow.
Figure 34. θ_JA vs Copper (1 Ounce) Area for the SO PowerPad Package
Increasing the copper area soldered to the DAP to 1 square inch of 1 ounce copper, using a dog-bone type
layout, will improve the θ_JA rating to 98°C/W. Figure 34 shows that increasing the copper area beyond 1 square
inch produces very little improvement.
Figure 35. Maximum Power Dissipation vs Ambient Temperature for the SO PowerPad Package
Figure 35 shows the maximum allowable power dissipation for the SO PowerPad package for a range of ambient
temperatures, assuming θ_JA is 98°C/W and the maximum junction temperature is 125°C.
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