ADV101 View Datasheet(PDF) - Analog Devices
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ADV101 Datasheet PDF : 12 Pages
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ADV101
The unused analog outputs should be terminated with the same
load as that for the used channel. In other words, if the red
channel is used and IOR is terminated with a doubly termi-
nated 75 Ω load (37.5 Ω), IOB and IOG should be terminated
with 37.5 Ω resistors. (See Figure 6.)
VIDEO
INPUT
R0
IOR
R7
IOG
G0
G7
B0
IOB
B7
ADV101
GND
DOUBLY
TERMINATED
75Ω LOAD
37.5Ω
37.5Ω
Figure 6. Input and Output Connections for Stand-Alone
Gray Scale or Composite Video
Video Output Buffers
The ADV101 is specified to drive transmission line loads, which
is what most monitors are rated as. The analog output configu-
rations to drive such loads are described in the Analog Interface
section and illustrated in Figure 5. However, in some applica-
tions it may be required to drive long “transmission line” cable
lengths. Cable lengths greater than 10 meters can attenuate and
distort high frequency analog output pulses. The inclusion of
output buffers will compensate for some cable distortion. Buff-
ers with large full power bandwidths and gains between 2 and 4
will be required. These buffers will also need to be able to sup-
ply sufficient current over the complete output voltage swing.
Analog Devices produces a range of suitable op amps for such
applications. These include the AD84X series of monolithic op
amps. In very high frequency applications (80 MHz), the
AD9617 is recommended. More information on line driver buff-
ering circuits is given in the relevant op amp data sheets.
Use of buffer amplifiers also allows implementation of other
video standards besides RS-343A and RS-170. Altering the gain
components of the buffer circuit will result in any desired video
level.
Z2
IOR, IOG, IOB
DACs
Z S = 75Ω
(SOURCE
TERMINATION)
Z1
+VS 0.1µF
27
AD848
34
6
0.1µF
– VS
Z O = 75Ω
75Ω
(CABLE)
GAIN
(G)
=
1
+
Z1
Z2
Figure 7. AD848 As an Output Buffer
Z L= 75Ω
(MONITOR)
REV. B
–9–
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