FMS6203_0611 Datasheet, PDF (7/9 Pages) Fairchild Semiconductor – Low-Cost 3-Channel Video Filter Driver for SD/PS/HD

Layout Considerations
General layout and supply bypassing play a major role in
high-frequency performance and thermal characteristics.
Fairchild offers a demonstration board to guide layout
and aid device evaluation. The demo board is a four-
layer board with full power and ground planes. Following
this layout configuration provides optimum performance
and thermal characteristics for the device. For the best
results, follow the steps and recommended routing rules
listed below.
Recommended Routing/Layout Rules
„ Do not run analog and digital signals in parallel.
„ Use separate analog and digital power planes to
supply power.
„ Traces should run on top of the ground plane at all-
times.
„ No trace should run over ground/power splits.
„ Avoid routing at 90-degree angles.
„ Minimize clock and video data trace length differ-
ences.
„ Include 10µF and 0.1µF ceramic power supply bypass
capacitors.
„ Place the 0.1µF capacitor within 0.1 inches of the
device power pin.
„ Place the 10µF capacitor within 0.75 inches of the
device power pin.
„ For multilayer boards, use a large ground plane to
help dissipate heat.
„ For two-layer boards, use a ground plane that extends
beyond the device body by at least 0.5 inches on all
sides. Include a metal paddle under the device on the
top layer.
„ Minimize all trace lengths to reduce series inductance.
Thermal Considerations
Since the interior of most systems, such as set-top-
boxes, TVs, and DVD players are at +70ºC; consider-
ation must be given to providing an adequate heat sink
for the device package for maximum heat dissipation.
When designing a system board, determine how much
power each device dissipates. Ensure that devices of
high power are not placed in the same location, such as
directly above (top plane) and below bottom plane) each
other on the PCB.
PCB Thermal Layout Considerations
„ Understand the system power requirements and envi-
ronmental conditions.
„ Maximize thermal performance of the PCB.
„ Consider using 70µm of copper for high-power
designs.
„ Make the PCB as thin as possible by reducing FR4
thickness.
„ Use vias in power pad to tie adjacent layers together.
„ Remember that baseline temperature is a function of
board area, not copper thickness.
„ Modeling techniques can provide a first-order approxi-
© 2006 Fairchild Semiconductor Corporation
FMS6203 Rev. 1.0.2
7
www.fairchildsemi.com