ml6427 Fairchild Semiconductor, ml6427 Datasheet - Page 6

• Manufacturer Part Number: ml6427
• Description: 75w Quad Video Cable Drivers And Filters With Switchable Inputs
• Manufacturer: Fairchild Semiconductor

ML6427
FUNCTIONAL DESCRIPTION
The ML6427 is a quad monolithic continuous time analog
video filter designed for reconstructing signals from four
video D/A sources. The ML6427 is intended for use in AC
coupled input and output applications.
The filters approximate a 4
characteristic with an optimization toward low overshoot
and flat group delay. All outputs are capable of driving
2V
of load capacitance at the output pin. They are also
capable of driving a 75W load at 1V
All channels are clamped during sync to establish the
appropriate output voltage swing range. Consequently the
input coupling capacitors do not behave according to the
conventional RC time constant. Clamping for all channels
settles within 10ms of a change in video sources.
Input coupling capacitors of 0.1µF are recommended for
all channels. During sync a feedback error amplifier
sources/sinks current to restore the DC level. The net result
is that the average input current is zero. Any change in the
value of the input coupling capacitors will linearly affect
the clamp response times.
The RGB channels have no pulldown current sources and
are essentially tilt-free. The inputs of the CV channels sink
less than 1µA during active video, resulting in a tilt of less
than 1mV for 220µF output capacitors. A 1000µF
capacitor is recommended for TV applications to minimize
tilt in the CV channels.
SWAP MULTIPLEXER CONTROL
Output pins CV
independently selectable among three input sources
(CV
state of digital inputs SWAP CVF, SWAP CVU, and A/B
MUX. This allows the two outputs to remain independent
and pass straight through, or to remain independent but
swapped, or for both outputs to have the same signal
sourcing from either CV
(See Table 1). If SWAP CVF is forced to logic low then
CV
THE CV
CV
OR THE CV
CV
If SWAP CVU is high then CV
from either the CV
SWAP CVF and SWAP CVU will pull low if they are not
driven.
The ML6427 is robust and stable under all stated load and
input conditions. Bypassing both V
ground ensures this performance. Two ML6427s can be
connected in a master-slave sync configuration. When
using this configuration (See Figure 6) only the “master”
ML6427 is required to have a signal with embedded sync
present on the CV
absence of sync on the CV
6
P-P
OUT
OUT
OUT
INU
into AC coupled 150W video loads with up to 35pF
/Y1
2/Y
1/Y
2/Y
INF
,
OUT
OUT
OUT
B/Y3 input. If SWAP CVU is logic low then
CV
INF
B is sourced from either the CV
A provides video from either the CV
B provides video from the CV
B/Y3 input. If SWAP CVF is logic high then
INF
OUT
A/Y2, or CV
INF
INF
1/Y
A/Y2 and CV
A/Y2 or the CV
OUT
INU
th
INF
A and CV
/Y1
-order Butterworth
OUT
A/Y2 and CV
INF
,
CV
B/Y3) depending on the
1/Y
INF
CC
INF
P-P
OUT
INF
B/Y3 inputs. In the
OUT
pins directly to
A/Y2, or CV
.
B/Y3 input. Both
2/Y
A provides video
INF
OUT
INU
B/Y3 inputs
INF
/Y1 input.
B are each
A/Y2 OR
INF
INF
B/Y3
A/Y2
the horizontal sync of either the CV
video sources ( i.e. , composite video plus RGB component
of the “slave” ML6427 it will have its SYNCIN input
connected to the SYNCOUT output of the “master”
ML6427.
SYNCIN AND SYNCOUT PINS
Each ML6427 has two sync detectors which control the
DC restore functions. The unfiltered channel has its own
detector, which controls the DC restore function during
the horizontal sync period of the CV
other sync detector controls the DC restore functions for
the filtered channels based upon the composite or luma
silgnal at the CV
Required Setup: A composite or luma or green signal
must be present on CV
provide necessary sync signals to other channels (R, G, B,
Y, C). Otherwise, sync must be provided at the SYNCIN
pin. For RGB applications the green channel with sync can
be used as an input to CV
The SYNCOUT pin provides a logic high when it detects
input (note that one input is selected by the A/B MUX pin).
The SYNCIN pin is an input for an external H-sync logic
signal to enable or disable the internal DC restore loop for
the filtered channels. When SYNCIN is logic high the DC
restore function is enabled.
For normal operation the SYNCOUT pin is connected to
the SYNCIN pin (see Figure 4). If neither the CV
nor the CV
sync can be applied on the SYNCIN pin. In master-slave
configurations the SYNCOUT of a ML6427 master can be
used as the SYNCIN of a ML6427 slave (see Figure 6).
VIDEO I/O DESCRIPTION
Each input is driven by either a low impedance source or
the output of a 75W terminated line. The input is required
to be AC coupled via a 0.1µF coupling capacitor which
gives a nominal clamping time of 10ms. All outputs are
capable of driving an AC coupled 150W load at 2V
1V
load capacitance can be driven without stability or slew
issues. A 220µF AC coupling capacitor is recommended at
the output to reduce power consumption. For DC coupled
outputs see the Typical Applications section.
ANALOG MULTIPLEXER CONTROL
The four filter channels each have two input multiplexers
which are paired to select between two four-channel
video). If A/B MUX is forced to logic high, it will select
Bank<A> of the video inputs (CV
Y6, B
Bank<B> of video inputs (CV
B
pull to logic high.
INF
P-P
B/C2) will be selected. If the A/B MUX is open it will
IN
into a 75W load. At the output pin, up to 35pF of
A/C1) to be enabled. If A/B MUX is logic low then
INF
B/Y3 has an embedded sync an external
INF
A/Y2 or CV
INF
A/Y2 or CV
INF
A/Y2 or CV
INF
INF
B/Y3, R
INF
B/Y3 input.
INF
A/Y2, R
INU
INF
A/Y2 or CV
IN
/Y1 input. The
B/Y3 inputs to
INF
B/Y5,G
B/Y3.
IN
A/Y4, G
INF
IN
INF
A/Y2
B/Y7,
P-P
B/Y3
IN
or
A/