el4331 Intersil Corporation, el4331 Datasheet - Page 10

• Manufacturer Part Number: el4331
• Description: Triple 2 1 Mux-amp Av = 1
• Manufacturer: Intersil Corporation

Photograph A3 shows the same circuit, with the counter
running at 25MHz. This turns out to be close to the limit of
the TTL counter used in the breadboard, rather than the limit
of the EL4331. Here the different glitches are easily
recognizable - a small glitch for one of the 4 input EL4331s
A/B switching, somewhat larger glitches when two banks
switch together, and the biggest glitch when all three banks
switch. Photograph A4 shows the big glitch in detail. A good
PCB and equal length and matched traces would clean up
these glitches.
Note: No supply bypass capacitors shown. Only one of three
channels shown.
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FIGURE 4. A SIMPLE 8:1 COMPONENT VIDEO
MULTIPLEXER
8-to-1 Multiplexer using Power-Down
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EL4331
Figure 4 shows one of the three channels of a component
video, 8:1 multiplexer. In this example, the power-down
capability is used to save on EL4331s, but as can be seen,
the control part does become more complicated. Using the
power-down mode for multiplexing does, of course, slow
down the speed with which one can select a given input
channel. However, if input channel selection can be done
during a blanking period, the couple of microseconds that it
takes to power-down one chip may be no problem. Note that
some external logic is needed in this application, both to
select the appropriate amplifier, and also to force a break-
before-make action by pulling the T_OFF line low. All this
logic would best be incorporated inside a PAL or gate array,
and is shown in gate form just to illustrate the idea. Note that
the BIT0 line would have the 3ns response time, since it is
switching the muxamps directly.
BIT2
0
0
0
0
1
1
1
1
TABLE 2. CHANNEL SELECTION TABLE
BIT1
0
0
1
1
0
0
1
1
BIT0
0
1
0
1
0
1
0
1
OUTPUT
SIG0
SIG1
SIG2
SIG3
SIG4
SIG5
SIG6
SIG7