FMS6143_07 Datasheet, PDF (9/11 Pages) Fairchild Semiconductor – Low-Cost Three-Channel 4th-Order Standard Defi nition Video Filter Driver

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 con-
figuration provides optimum performance and thermal
characteristics for the device. For the best results, follow the
steps and recommended routing rules listed below.
Thermal Considerations
Since the interior of most systems, such as set-top boxes,
TVs, and DVD players, are at +70ºC; consideration must be
given to providing an adequate heat sink for the device pac-
kage for maximum heat dissipation. When designing a sys-
tem board, determine how much power each device dissipa-
tes. 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.
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 differences.
■ 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.
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 power pad to tie adjacent layers together.
■ Remember that baseline temperature is a function of
board area, not copper thickness.
■ Modeling techniques provide a first-order approximation.
© 2006 Fairchild Semiconductor Corporation
FMS6143 Rev. 4.0.5
9
www.fairchildsemi.com