LM2830, LM2830-Q1

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SNVS454E – AUGUST 2006 – REVISED DECEMBER 2014

Layout Example (continued)

Figure 30. PCB Layout Example

10.3 Thermal Considerations

The PCB size, weight of copper used to route traces and ground plane, and number of layers within the PCB can

greatly effect RθJA. The type and number of thermal vias can also make a large difference in the thermal

impedance. Thermal vias are necessary in most applications. They conduct heat from the surface of the PCB to

the ground plane. Four to six thermal vias should be placed under the exposed pad to the ground plane if the

WSON package is used.

Thermal impedance also depends on the thermal properties of the application operating conditions (Vin, Vo, Io

etc), and the surrounding circuitry.

Silicon Junction Temperature Determination Method 1:

To accurately measure the silicon temperature for a given application, two methods can be used. The first

method requires the user to know the thermal impedance of the silicon junction to top case temperature.

Some clarification needs to be made before we go any further.

RθJC is the thermal impedance from all six sides of an IC package to silicon junction.

RΦJC is the thermal impedance from top case to the silicon junction.

In this data sheet we will use RΦJC so that it allows the user to measure top case temperature with a small

thermocouple attached to the top case.

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