EL4332 查看數據表（PDF） - Intersil
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EL4332 Datasheet PDF : 15 Pages
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EL4332
FIGURE 26. TYPICAL CONNECTION FOR A 2:1 COMPONENT VIDEO MULTIPLEXER
Applications Information
Figure 26 shows a typical use for the EL4332. The circuit is a
component video (R,G, B or Y,U,V) multiplexer. Since the
gain of the internal amplifiers has been set to 2, the only
extra components needed are the supply decoupling
capacitors and the back terminating resistors, if transmission
lines are to be driven. The EL4332 can drive backmatched
50Ω or 75Ω loads.
Grounds
It will be noticed that each mux-amp channel has its own
separate ground pin. These ground pins have been kept
separate to keep the channel separation inside the chip as
large as possible. The feedback resistors use these ground
pins as their reference. The resistors total 400Ω, so there is
a significant signal current flowing from these pins to ground.
The ground pins should all be connected together, to a
ground plane underneath the chip. 1 oz. copper for the
ground plane is highly recommended.
Further notes and recommended practices for high speed
printed circuit board layout can be found in the tutorials in
the Elantec databooks.
Supplies
Supply bypassing should be as physically near the power
pins as possible. Chip capacitors should be used to
minimize lead inductance. Note that larger values of
capacitor tend to have larger internal inductances. So when
designing for 3 transmission lines or similar moderate loads,
a 0.1µF ceramic capacitor right next to the power pin in
parallel with a 22µF tantalum capacitor placed as close to
the 0.1µF is recommended. For lighter loadings, or if not all
the channels are being used, a single 4.7µF capacitor has
been found quite adequate.
Note that component video signals do tend to have a high
level of signal correlation. This is especially true if the video
signal has been derived from 3 synchronously clocked
DACs. This corresponds to all three channels drawing large
slew currents simultaneously from the supplies. Thus, proper
bypassing is critical.
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