FMS6243 Datasheet, PDF (8/10 Pages) Fairchild Semiconductor – Low-Cost, 3-Channel, SD Video Filter Drivers with External Delay Control

Layout Considerations
It is critical that the delay capacitor pins (1, 7, and 9)
have the delay capacitor placed as close to the device
pin as possible. The ground connection should be as
short as possible, ideally a direct connect to the adjacent
ground pin. These layout considerations create the best
environment for the device and reduce noise.
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 multi-layer boards, use a large ground plane to
help dissipate heat.
■ For two-layer boards, use a ground plane that extends
beyond the device body 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 +70°C; 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) or below (bottom plane), each
other on the PCB.
PCB Thermal Layout Considerations
■ Understand the system power requirements and
environmental 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 the power pad to tie adjacent layers
together.
■ Remember that baseline temperature is a function of
board area, not copper thickness.
■ Modeling techniques provide first-order approximation.
© 2007 Fairchild Semiconductor Corporation
FMS6243 Rev. 1.0.0
8
www.fairchildsemi.com