ml6429 Fairchild Semiconductor, ml6429 Datasheet - Page 8
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ml6429
Manufacturer Part Number
ml6429
Description
Quad Video Cable Drivers Filters With Switchable Inputs
Manufacturer
Fairchild Semiconductor
Datasheet
1.ML6429.pdf
(15 pages)
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TYPICAL APPLICATIONS
BASIC APPLICATIONS
The ML6429 provides channels for two banks of inputs for
RGB and composite video. The R and G channels can be
used as luma inputs while the B channel can be used as a
chroma input. Composite outputs and an H-sync output is
also provided. There are several configurations available
with the ML6429. Figure 4 includes a list of basic output
options for composite, S-video, TV modulator, and RGB
outputs. Note that each composite channel can drive a CV
load or a channel modulator simultaneously. The ML6429
standalone can be used as an EVC or SCART cable driver
with nine video sources (75Ω or low impedance buffer)
and seven video outputs. All inputs and outputs are AC
coupled. When driving seven loads, power dissipation
must be measured to ensure that the junction temperature
doesn't exceed 120ºC.
EVC CABLE DRIVING
The ML6429 can be configured to drive composite video,
S-video, and horizontal sync through an EVC connector
(Figure 5). Composite video and S-video inputs are filtered
through 4
internal 75Ω cable drivers. A buffered H-sync output is
also available.
SCART CABLE DRIVING
The ML6429 can be configured either as a SCART cable
driver (Figure 4) or as a SCART cable driver and S-video
driver (Figure 6). A horizontal sync output is also available.
Note that the ML6429 can be used in a master-slave mode
where the sync-out from the master is used as the sync-in
of the slave; this allows the CV, S-video, and RGB channels
to operate under the same sync signals.
Note that in SCART applications, it is not always necessary
to AC couple the outputs. Systems using SCART
connectors for RGB and composite video can typically
handle between 0 and 2V DC offset (see DC Coupled
Applications section).
RGB APPLICATIONS
RGB video can be filtered and driven through the
ML6429. For sync suppressed RGB, the sync signal can be
derived from SYNCIN PIN.
OSD (ON-SCREEN DISPLAY) APPLICATIONS
Unfiltered RGB video from an OSD processor needs to be
filtered and then synchronized to a fast blanking interval
or alpha-key signal for later video processing. With the
total filter delay being 80ns ±10ns, a D flip-flop or similar
delay element can be used to delay the fast blanking
interval or alpha-key signal, which synchronizes the RGB
and OSD signals (Figure 9).
8
th
-order Butterworth filters and driven through
CHANNEL MULTIPLEXING
The ML6429 can be configured for multiple composite
channel multiplexing (Figure 8). Composite and RGB
sources such as VCRs, and digital MPEG 2 sources can be
selected using the ML6429 swap mux controls. A/B MUX,
SWAP CVU, and SWAP CVF signals can be used to select
and route from various input sources.
DC COUPLED APPLICATIONS
The 220µF capacitor coupled with the 150Ω termination
forms a highpass filter which 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 ML6429 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 one 75Ω load per output. However,
if two loads are required to be driven at a time on the
composite output while DC coupling is used, then the
swap–mux and 5
the filtered composite signal on both the 4
drivers. Thus, the composite load driving requirement is
divided into two line drivers versus one.
Required Setup: A composite or luma or green signal must
be present on CV
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
USING THE ML6429 FOR PAL APPLICATIONS
The ML6429 can be optimized for PAL video by adding
frequency peaking to the composite and S-video outputs.
Figure 10 illustrates the use of a additional external
capacitor (300pF), added in parallel to the output source
termination resistor. This raises the frequency response
from 1.0dB down at 4.8MHz (for no peaking cap) to 0.2dB
down at 4.8MHz (for 300 pF), which allows for accurate
reproduction of the upper sideband of the PAL subcarrier.
Figure 11 shows the frequency response of PAL video with
various values of peaking capacitors (0pF, 220pF, 270pF,
300pF) between 0 and 10MHz.
For NTSC applications without the peaking capacitor, the
rejection at 27MHz is 40dB (typical). For PAL applications
with the peaking capacitor, the rejection at 27MHz is
34dB (typical). (Figure 12). The differential group delay is
shown in Figure 13 with and without a peaking capacitor
(0pF, 220pF, 270pF, and 300pF) varies slightly with
capacitance; from 8ns to 13ns.
th
INU
line driver can be configured to enable
A/Y2 or CV
INU
A/Y2 or CV
INU
B/Y3 inputs to provide
INU
B/Y3.
REV. 1.1 2/8/2001
th
and 5
th
line