AN-42041 Datasheet, PDF (1/5 Pages) Fairchild Semiconductor – 5th-Order S-Video Filter/Driver Reduces NTSC/PAL System Parts Count

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AN-42041
5th-Order S-Video Filter/Driver
Reduces NTSC/PAL System Parts Count
Introduction
The FMS6400 IC is an 8-pin, SOIC, 5th-order, dual video fil-
ter designed to replace bulky discrete passive filters (Figure 1)
or the handful of video integrated circuits commonly required
to properly reconstruct DAC-generated video signals.
The FMS6400 operates from a single +5V ± 5% supply. In
addition to Y/C filtering of DAC outputs, the FMS6400 contains
circuitry for sync tip clamping and restoration. Further, the
filters internally sum the luma and chroma channels, provid-
ing a third filtered output: the composite video signal.
The FMS6400 is designed for AC- or DC-coupled output
applications, but requires capacitive coupling (0.1μF) of the
input signals. All output channels are fully buffered, capable
of driving 2V_pp into a 150Ω load or 1V_pp into a 75Ω load. The
FMS6400 also offers gain selections of 0dB or 6dB. This
provides flexibility to drive directly into an ADC, limiting the
number of discrete components. The FMS6400 is fully pro-
tected from load shorting, providing the maximum junction
temperature of the part is not exceeded, and may drive two
separate loads each.
This application note contains performance results and design
information collected from an FMS6400 design utilizing a
four-layer PC board. The schematic of the board used to eval-
uate this device is shown in Figure 9.
Application Board Testing
Test Equipment
■ One power supply: 5V ±10%, 200mA maximum
■ One 14-inch (or larger), high-resolution CRT monitor:
Sony PVM-14M2U
■ One Y/C video signal source:
JVC HR-S7100UV VCR set for “Live Feed” from a
local television station
■ One HP 3577A network analyzer
■ One Tektronix TDS640A oscilloscope
■ One FMS6400 demo board
■ Assorted video cables
75Ω
YIN
DAC
75Ω
X2
VREF
75Ω ^220µF
YOUT
75Ω ^220µF
X2
75Ω ^220µF
CVOUT1
CVOUT2
75Ω
CIN
DAC
75Ω
75Ω ^220µF
COUT
X2
May be
AC or DC
coupled
* FMS6400 also conatins sync
tip clamp and feedback
amplifier for ainti-clipping
Figure 1. S-Video Filter Discrete Solution
© 1999 Fairchild Semiconductor Corporation
AN-42041 Rev. 1.0.1
www.fairchildsemi.com