SGM9146 Datasheet, PDF (10/13 Pages) SG Micro Corp – 4-Channel, Video Filter Driver

SGM9146
4-Channel, Video Filter Driver
for SD/HD (1080i)/HD (1080p)
APPLICATION INFORMATION
Output Considerations
The selection of the coupling capacitor is a function of the
subsequent circuit input impedance and the leakage current of
the input being driven. In order to obtain the highest quality
output video signal the series termination resistor must be
placed as close to the device output pin as possible. This
greatly reduces the parasitic capacitance and inductance effect
on the SGM9146 output driver. Recommended distance from
device pin to series termination resistor should be no greater
than 0.1 inches.
75Ω series termination resistor
0.1
Recommended Routing/Layout Rules
 Do not run analog and digital signals in parallel.
 Use separate analog and digital power planes to supply
power.
 Do not run traces on top of the ground plane.
 Run no traces over ground/power splits.
 Avoid routing at 90-degree angles.
 Minimize clock and video data trace length differences.
 Include 0.01μF and 0.1μF ceramic power supply bypass
capacitors.
 Place the 0.1μF capacitor within 0.1 inches of the device
power pin.
 Place the 0.01μF 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.
 Place a 75Ω series resistor within 0.5 inches of the output pin
to isolate the output driver from board parasitics.
Figure 4. Distance from Device Pin to Series Termination
Resistor
Thermal Considerations
Since the interior of systems such as set-top boxes, TVs and
DVD players are at +70℃, consideration 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 for 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.
 Consider modeling techniques a first-order approximation.
Layout Considerations
General layout and supply bypassing play a major role in
high-frequency performance and thermal characteristics. We
offer 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.
SG Micro Corp
10
www.sg-micro.com