www.fairchildsemi.com
FMS6410
Dual Channel Video Drivers with Integrated Filters
and Composite Video Summer
Video Features
• Dual integrated video low pass reconstruction filters on
outputs
• Composite Video Summer
• Integrated output drivers provide low impedance outputs
and deliver 2V
P-P
(6dB gain) video into 150Ω.
• 7.1MHz 4
th
order video filters
• 7.1MHz Y and C filters, with CV out
• 42dB stopband attenuation at 27MHz on Y, C, and CV
• Better than 1dB flatness to 4.5 MHz on Y, C, and CV
• No external frequency select components or clocks
• 9ns group delay flatness on Y, C, and CV output
• AC coupled inputs and outputs
• 0.4% differential gain with 0.4° differential phase
• Integrated DC Restore / Clamp circuitry with low tilt
General Description
The FMS6410 Dual Channel Video Filter – Driver Chip with
CV Summer offers comprehensive video filtering for set top
box or DVD applications. This part consists of two 4
th
order
Butterworth 7.1MHz low pass filters for video signals. The
filters are optimized for low overshoot and flat group delay.
The device also contains a summing circuit to generate
filtered composite video.
Integrated video drivers are
included to facilitate a direct drive to the outside world.
In a typical application, the Y and C input signals from
DACs are AC coupled into the filter. Both channels have DC
restore circuitry to clamp the DC input levels during video
sync. The Y and C channels use a separate feedback clamp.
The clamp pulse is derived from the Y channel.
The outputs are AC coupled. The Y, C and, CV outputs are
buffered to drive 2V
P-P
into a 150Ω load (1V
P-P
into a
doubly terminated 75Ω coax load) with up to 35pF of load
capacitance at the output pin. The Y, C, and CV channels
have a gain of approximately 2 (6dB) with 1V
P-P
input
levels. There is an option for the video output to be DC
coupled which limits the drive output to one output on each
channel.
Applications
•
•
•
•
•
•
•
CCTV
Cable and Satellite Set top boxes
DVD players
Televisions
Personal Video Recorders (PVRs)
Video On Demand (VOD)
Distribution Amplifiers
Functional Block Diagram
SYNC STRIP, REF,
AND TIMING
6dB
1
YIN
YOUT 8
gM
2
1V
DNC
(Do Not Connect)
VCC_VIDEO
7
FMS6410
3
GND_VIDEO
CVOUT 6
gM
1V
4
CIN
6dB
COUT 5
REV. 2a February 2004
DATA SHEET
FMS6410
Functional Description
Introduction
The FMS6410 is a dual monolithic continuous time video
filter designed for reconstructing the luminance and chromi-
nance signals from an S-Video D/A source. The Composite
video output is generated by summing the filtered Y and C
outputs. The chip is intended for use in applications with AC
coupled inputs and AC coupled outputs (See Figure 1). The
reconstruction filters approximate a 4th-order Butterworth
characteristic with an optimization toward low overshoot and
flat group delay. Y, C, and CV outputs are capable of driving
2V
P-P
into AC coupled 150Ω video loads with up to 35pF of
load capacitance at the output pin. All channels are clamped
during sync to establish the appropriate output voltage swing
range. Thus the input coupling capacitors do not behave
according to the conventional RC time constant. Clamping
for all channels settles to less than 10mv within 5ms of a
change in video input sources. In most applications the input
coupling capacitors are 0.1µF. The Y and C inputs typically
sink 1µA during active video, which nominally tilts a
horizontal line by about 2mV at the Y output. During sync,
the clamp typically sources 20µA to restore the DC level.
The net result is that the average input current is zero.
Any change in the input coupling capacitor’s value will
inversely alter the amount of tilt per line. Such a change will
also linearly affect the clamp response times. This product is
robust and stable under all stated load and input conditions.
Capacitive bypassing of V
CC
directly to ground ensures this
performance.
Chrominance (C) I/O
The chroma input is driven by a low impedance source of
0.7V
P-P
or the output of a 75Ω terminated line. The input is
required to be AC coupled via a 0.1µF coupling capacitor
which allows for a clamp setting time of 5ms. The chroma
output is capable of driving an AC coupled 150Ω load at
2V
P-P
, or 1V
P-P
into a doubly terminated 75Ω load. Up to
35pF of load capacitance can be driven without stability or
slew issues. A 0.1µF AC coupling capacitor is recommended
at the output. Since chrominance signals do not contain
low frequency components, the smaller 0.1µF cap is
recommended instead of the 220µF cap to reduce circuit
cost.
Composite Video (CV) Output
The composite video output is capable of driving 2 loads to
2V
P-P
. It is intended to drive a TV and a VCR. Either the TV
input or the VCR input can be shorted to ground and the
other output will still meet specifications. Up to 35pF of load
capacitance (at the output pin) can be driven without stability
or slew issues.
DC Coupled Output Applications
The 220µF capacitor coupled with the 150Ω termination
forms a high pass filter that blocks the DC while passing the
video frequencies and avoiding tilt. Lower values such as
10µF would create a problem. By AC coupling, the average
DC level is zero. Thus, the output voltages of all channels
will be centered around zero. Alternately, DC coupling the
output of the FMS6410 is allowable. There are several
tradeoffs: The average DC level on the outputs will be 2V;
Each output will dissipate an additional 40mW nominally;
The application will need to accommodate a 1V DC offset
sync tip; And it is recommended to limit each output to one
150Ω load.
Luminance (Y) I/O
The luma input is driven by either a low impedance source of
1V
P-P
or the output of a 75Ω terminated line. The input is
required to be AC coupled via a 0.1µF coupling capacitor
which allows for a settling time of 5ms. The luma output is
capable of driving an AC coupled 150Ω load at 2V
P-P
, or
1V
P-P
into a doubly terminated 75Ω load. Up to 35pF of
load capacitance (at the output pin) can be driven without
stability or slew issues. The output is AC coupled with a
220µF or larger AC coupling capacitor.
REV. 2a February 2004
3
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