LP38513-ADJ Datasheet, PDF (12/18 Pages) National Semiconductor (TI) – 3A Fast-Transient Response Adjustable Low-Dropout Linear Voltage Regulator

LP38513-ADJ
SNVS514C – JANUARY 2009 – REVISED APRIL 2013
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LP38513-ADJ is available in the TO-263 THIN surface mount package. For a comparison of the TO-263 THIN
package to the standard TO-263 package see Application Note AN-1797 TO-263 THIN Package SNVA328. The
thermal resistance depends on amount of copper area, or heat sink, and on air flow. See Application Note AN-
1520 A Guide to Board Layout for Best Thermal Resistance for Exposed Packages SNVA183 for guidelines.
Heat-Sinking the TO-263 THIN Package
The DAP of the TO-263 THIN package is soldered to the copper plane for heat sinking. The TO-263 THIN
package has a θ_JA rating of 67°C/W, and a θ_JC rating of 2°C/W. The θ_JA rating of 67°C/W includes the device
DAP soldered to an area of 0.055 square inches (0.22 in x 0.25 in) of 1 ounce copper on a two sided PCB, with
no airflow. See JEDEC standard EIA/JESD51-3 for more information.
Figure 19 shows a curve for the θ_JA of TO-263 THIN package for different thermal via counts under the exposed
DAP, using a four layer PCB for heat sinking. The thermal vias connect the copper area directly under the
exposed DAP to the first internal copper plane only. See JEDEC standards EIA/JESD51-5 and EIA/JESD51-7 for
more information.
Figure 19. θ_JA vs Thermal Via Count for the TO-263 THIN Package on 4–Layer PCB
Figure 20 shows the thermal performance when the Thin TO-263 is mounted to a two layer PCB where the
copper area is predominately directly under the exposed DAP. .As shown in the figure, increasing the copper
area beyond 1 square inch produces very little improvement.
Figure 20. θ_JA vs Copper Area for the TO-263 THIN Package
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