Fairchild Semiconductor ML6415 Datasheet
www.fairchildsemi.com
ML6415
S-Video Filter with Summed Composite Output,
Sound Trap, and Group Delay Compensation
Features
• 7.1MHz Y and C filters, with CV out
• 14dB notch at 4.5MHz for sound trap
• 42dB stopband attenuation at 27MHz on Y, C, and CV
• Better than 1dB flatness to 4.5 MHz on Y, C, and CV
• RF Modulator output differential group delay between
400kHz and 3.58MHz is typically -170ns.
• 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 on Y, C and CV channels, 0.4º
differential phase on Y, C and CV channels
• 0.8% total harmonic distortion on all channels
• DC restore with low tilt
Applications
• Cable Set-top Boxes
• Satellite Set-top Boxes
•DVD Players
Block Diagram
General Description
The ML6415 is a dual Y/C 4th-order Butterworth lowpass
video filter optimized for minimum overshoot and flat group
delay. The device also contains a summing circuit to generate filtered composite video, an audio trap and group delay
compensation circuit to notch-out audio, providing an area
for the addition of the FM audio carrier(s) and mimic the
group delay distortion introduced at the transmitter. The
group delay predistortion compensates for the nominal TV
receiver IF filter distortion.
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, CV, and modulator
outputs can drive 2V
load). The Y, C, CV, and notch channels have a gain of
approximately 2 (6dB) with 1V
into a 150 Ω load (1V
pp
input levels.
pp
75 Ω coax
pp
YIN
CIN
VCC
7
SYNC STRIP,
REFERENCE,
AND TIMING
1
4
4TH – ORDER
FILTER
gM
1V
gM
4TH – ORDER
FILTER
1V
+
Σ
+
×2
×2
3
GND
×2
NOTCH,
GROUP
DELAY
8
6
2
5
YOUT
CVOUT
RF MOD
COUT
REV. 2F May 2003
ML6415 DATA SHEET
Pin Configuration
ML6415
8-Pin SOIC (S08)
YIN
RF MOD
GND
CIN
1
2
3
4
TOP VIEW
8
YOUT
7
VCC
6
CVOUT
5
COUT
Pin Descriptions
Pin # Signal Name Description
1 YIN Luminance input
2 RF MOD Output to RF modulator driver
3 GND Ground
4 CIN Chrominance input
5 COUT Chrominance output
6CVOUT Composite video output
7 VCC 5V supply
8YOUT Luminance output
Functional Description
Introduction
This product is a dual monolithic continuous time video filter
designed for reconstructing the luminance and chrominance
signals from an S-Video D/A source. Composite video output is generated by summing the Y and C outputs. The chip
is intended for use in applications with AC coupled input 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
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 input typically sinks 1µA during active video,
into AC coupled 150 Ω video loads, with up
pp
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 VCC directly to
ground ensures this performance.
Luminance (Y) I/O
The luma input is driven by either a low impedance source of
1V
or the output of a 75 Ω terminated line. The input is
P-P
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 150 Ω load at 2V
1V
into a 75 Ω load. Up to 35pF of load capacitance
pp
(at the output pin) can be driven without stability or slew
issues. The output is AC coupled with a 400µF or larger AC
coupling capacitor.
pp
, or
2
REV. 2F May 2003
DATA SHEET ML6415
Chrominance (C) I/O
The chroma input is driven by a low impedance source of
0.7V
or the output of a 75 Ω terminated line. The input is
pp
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 150 Ω load at
2V
P-P
, or 1V
into a 75 Ω load. Up to 35pF of load capaci-
P-P
tance can be driven without stability or slew issues. A 0.1µF
AC coupling capacitor is recommended at the output.
(This reduces the circuit cost as chroma does not contain
low frequency components.)
Typical Applications Diagram
4.5MHz FM SOUND
+
NOTCH
YIN
ENCODER
CIN
5.0V
0.1µF
0.1µF
1
4
4th-ORDER
FILTER
+
Σ
+
4th-ORDER
FILTER
AND GROUP
DELAY
PROTECTION
37
2
Σ
220µF
8
6
5
220µF
220
220µF
Composite Video (CV) Output
The composite video output is capable of driving 2 loads to
2V
. It is intended to drive a TV and a VCR. Either the TV
P-P
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.
RF Modulator Output
The RF modulator output is capable of driving a 600 Ω load
to 2V
VIDEO MODULATOR
75Ω
75Ω
µF
75Ω
75Ω
, but is primarily intended to drive a modulator load.
P-P
TO CHANNEL 3 OR 4
VIDEO CABLES
75Ω
75Ω
75Ω
75Ω
YOUT
CVOUT TO TV
CVOUT TO VCR
COUT
Figure 1. Coupled S-Video, Composite Video Line Driver, Sound Trap, and Group Delay Pre-distortion
REV. 2F May 2003
1µF0.1µF
3
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