LP38502-ADJ Datasheet, PDF (18/27 Pages) Texas Instruments – LP3850x-ADJ, LP3850xA-ADJ 1.5-A Flexcap Low-Dropout Linear Regulatorfor 2.7-V to 5.5-V Inputs

LP38500-ADJ, LP38502-ADJ
SNVS539G – NOVEMBER 2007 – REVISED JUNE 2015
Layout Examples (continued)
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EN
Pull-up
Resistor
IN
Input
Capacitor
R2
ADJ
R1
OUT
Output
Capacitor
Ground
Figure 23. LP38502-ADJ TO-263 Layout
10.2.1 Heatsinking WSON Package
The junction-to-ambient thermal resistance for the WSON package is dependent on how much PCB copper is
present to conduct heat away from the device. The LP38502SD-ADJ evaluation board (980600046-100) was
tested and gave a result of about 52.5°C/W with a power dissipation of 1 W and no external airflow. This
evaluation board is a two layer board using two ounce copper, and the copper area on topside for heatsinking is
approximately two square inches. Multiple vias under the DAP also thermally connect to the backside layer which
has about three square inches of copper dedicated to heatsinking.
With four thermal vias directly under the DAP to the first copper plane, the modeling predicts a R_θJA of 52.5°C/W.
Adding a dog-bone copper area with four additional thermal vias in the dog-bone area to the first copper plane
can improve R_θJA to 45°C/W.
See Application Note AN-1520 A Guide to Board Layout for Best Thermal Resistance for Exposed Packages
(SNVA183) for additional thermal considerations for printed circuit board layouts.
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