CM3212 Datasheet, PDF (10/11 Pages) ON Semiconductor – VTT Termination Voltage Regulator

CM3212
APPLICATION INFORMATION (Cont’d)
PCB Layout Considerations
The CM3212 has a heat spreader (exposed pad) attached to the bottom of the WDFN8 package in order for the heat to be
transferred more easily from the package to the PCB. The heat spreader is a copper pad with slightly smaller dimensions than
the package itself. By positioning the matching pad on the PCB top layer to connect to the spreader during manufacturing, the
heat will be transferred between the two pads. Thermal Layout for WDFN8 package shows the CM3212 recommended PCB
layout. Please note there are four vias to allow the heat to dissipate into the ground and power planes on the inner layers of the
PCB. Vias must be placed underneath the chip but this can result in solder blockage. The ground and power planes need to be
at least 2 square inches of copper by the vias. It also helps dissipation if the chip is positioned away from the edge of the PCB,
and away from other heat−dissipating devices. A good thermal link from the PCB pad to the rest of the PCB will assure the
best heat transfer from the CM3212 to ambient temperature.
Top View
Bottom Layer
Ground Plane
Top Layer Copper
Connects to Heat Spreader
Pin Solder Mask
Vias ( 0. 3 mm Diameter )
Thermal PAD
Solder Mask
Figure 2. Thermal Layout for WDFN8 Package
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