lm25117psqx National Semiconductor Corporation, lm25117psqx Datasheet - Page 20

• Manufacturer Part Number: lm25117psqx
• Description: Wide Input Range Synchronous Buck Controller With Analog Current Monitor
• Manufacturer: National Semiconductor Corporation

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The LM25117 has an exposed thermal pad to aid power dis-
sipation. Adding several vias under the exposed pad helps
conduct heat away from the IC. The junction to ambient ther-
mal resistance varies with application. The most significant
variables are the area of copper in the PC board, the number
of vias under the exposed pad and the amount of forced air
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cooling. The integrity of the solder connection from the IC ex-
posed pad to the PC board is critical. Excessive voids greatly
decrease the thermal dissipation capacity.
The highest power dissipating components are the two power
switches. Selecting NMOS switches with exposed pads aids
the power dissipation of these devices.