eorex
Thermal Considerations
EP3102
The SOP-8 package needs a heat sink under most conditions. The size of the heat-sink depends on the
input voltage, the output voltage, the load current and the ambient temperature. The EP3102 junction
temperature rises above ambient temperature for a 2A load and different input and output voltages.
The data for these curves was taken with the EP3102 operating as a buck switching regulator in an
ambient temperature of 25°C (still air). These temperature increments are all approximate and are
affected by many factors. Some of these factors include board size, shape, thickness, position, location,
and even board temperature. Other factors are traced width, total printed circuit copper area, copper
thickness, single or double-sided, multi-layer board and amount of solder on the board. Higher ambient
temperatures require more heat sinking.
For the best thermal performance, wide copper traces and generous amounts of printed circuit board
copper should be used in the board layout. (One exception is the out (switch) pin, which should not have
large areas of copper.) Large areas of copper provide the best transfer of heat (lower thermal resistance)
to the surrounding air, and moving air lowers the thermal resistance even further.
The effectiveness of the PC board to dissipate heat also depends on the size, quantity and spacing of
other components on the board, as well as whether the surrounding air is still or moving. Furthermore,
some of these components such as the catch diode will add heat to the PC board and heat can vary as
the input voltage changes. For the inductor, depending on the physical size, type of core material and the
DC resistance, it could either act as a heat sink taking heat away from the board, or it could add heat to
the board.
Nov. 2006
9/10
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