ML6428 Datasheet, PDF (1/10 Pages) Fairchild Semiconductor – S-Video Filter and 75 Ω Line Drivers with Summed Composite Output

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ML6428
S-Video Filter and 75Ω Line Drivers with Summed
Composite Output
Features
• 6.7MHz Y and C filters, with CV out for NTSC or PAL
• 75Ω cable line driver for Y, C, CV, and TV modulator
• 43dB stopband attenuation at 27MHz
• 1dB flatness up to 4.8MHz
• No external frequency select components or clocks
• 12ns group delay flatness up to 10MHz
• 5% overshoot on any input edge
• AC coupled input and output (ML6428CS-1)
• AC coupled input and DC coupled output
(ML6428CS-2)
• 0.4% differential gain on all channels, 0.4º differential
phase on all channels
• 0.7% total harmonic distortion on all channels
• 5V ±10% operation
• DC restore with low tilt
General Description
The ML6428 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 gener-
ate filtered composite video.
The Y and C input signals from DACs are AC coupled into
the ML6428. Both channels have DC restore circuitry to
clamp the DC input levels during video sync. The Y channel
uses a sync tip clamp. The CV and the C channels share a
feedback clamp.
All outputs must be AC coupled into their loads for the -1
version. The -2 version must be DC coupled. All inputs (-1
and -2 versions) are AC coupled. The Y or C outputs can
drive 2VP-P into a 150Ω load, while the CV output can drive
2VP-P into 75Ω. Thus the CV output is capable of driving
two independent 150Ω loads to 2VP-P.
On the CV output, one of the 75Ω loads can be shorted to
ground with no loss of drive to the remaining load. The Y, C
and CV channels have a gain of 2 (6dB) with 1VP-P input
levels.
Block Diagram
VCC
2
VCCO
7
YIN ₁
4th-ORDER
FILTER
+
SYNC TIP CLAMP
Σ
TRANSCONDUCTANCE
+
ERROR AMP
CIN 4
4th-ORDER
FILTER
3
GND
BUFFER
8 _YOUT
BUFFER
6 _CVOUT
BUFFER
5 _COUT
REV. 1B April 2003