SGM9116_17 Datasheet, PDF (7/11 Pages) SG Micro Corp – Triple, 38.5MHz, 6th-Order HDTV Video Filter Driver

SGM9116
Triple, 38.5MHz, 6th-Order
HDTV Video Fliter Driver
APPLICATION INFORMATION
Functional Description
SGM9116 operates from a single 3.3V to 5.5V supply.
In application, SGM9116 is a fully integrated solution
for filtering and buffering HDTV signals in front of video
decoder or behind video encoder. For example,
SGM9116 can replace three passive LC filters and
three amplifier drivers at R\G\B and Y\Pb\Pr output side
in set-top box and DVD player. This solution can help
reduce PCB size and production cost, and it also
improves video signal performance comparing with
traditional design using discrete components.
SGM9116 features a DC-coupled input buffer, a
6th-order low-pass filter to eliminate out-of-band noise
of video encoder, and a gain of 6dB in the output
amplifier to drive 75Ω load. The AC- or DC-coupled
input buffer eliminates sync crush, droop, and field tilt.
The output of SGM9116 also can be DC-coupled or
AC-coupled.
Input Considerations
Besides AC coupling, the SGM9116 inputs also can be
DC-coupled. In DC coupling application, no input
coupling capacitors are needed because the amplitude
of input video signal from DAC includes ground and
extends up to 1.4V, and SGM9116 can be directly
connected to the output of a single-supply,
current-output DAC without any external bias network.
In applications where DAC’s output level exceeds the
range from 0V to 1.4V, or SGM9116 is driven by an
unknown external source or a SCART switch which has
its own clamping circuit, AC coupling is needed.
Output Considerations
The SGM9116 outputs can be DC-coupled or
AC-coupled. When input is 0V, the SGM9116 output
voltage is 494mV typically. In DC coupling design, one
75Ω resistor is used to connect SGM9116’s output pin
with external load directly, and this serial back-termination
resistor is used to match the impedance of the
transmission line between SGM9116 and external load
to cancel the signal reflection. The SGM9116 outputs
can sink and source current allowing the device to be
AC-coupled with external load. In AC coupling, at least
220µF capacitor will be used in order to eliminate field
tilt.
Power-Supply Bypassing and Layout
Correct power supply bypassing is very important for
optimizing video performance in design. One 0.1µF and
one 10µF capacitors are always used to bypass +V_S
pin of SGM9116. Place these two capacitors as close
to the SGM9116 supply pin as possible. A large ground
plane is also needed to ensure optimum performance.
The input and output termination resistors should be
placed as close to the related pins of SGM9116 as
possible to avoid performance degradation. The PCB
traces at the output side should have 75Ω characteristic
impedance in order to match the 75Ω characteristic
impedance of the cable connecting external load. In
design, keep the board trace at the inputs and outputs
of the SGM9116 as short as possible to minimize the
parasitic stray capacitance and noise pickup.
SG Micro Corp
www.sg-micro.com
MARCH 2017
7