Manual

The MAX4028/MAX4029 have a fixed gain of +2V/V that
is internally set with two 1kΩ thin-film resistors. The
impedance of the internal feedback resistors must be
taken into account when operating multiple MAX4028/
MAX4029s in large multiplexer applications.
Applications Information
Video Line Driver
The MAX4028/MAX4029 are well suited to drive coaxial
transmission lines when the cable is terminated at both
ends, as shown in Figure 3, where the fixed gain of
+2V/V compensates for the loss in the resistors, R
T
.
Driving Capacitive Loads
A correctly terminated transmission line is purely resis-
tive and presents no capacitive load to the amplifier.
Reactive loads decrease phase margin and may pro-
duce excessive ringing and oscillation.
Another concern when driving capacitive loads is the
amplifier’s output impedance, which appears inductive
at high frequencies. This inductance forms an L-C reso-
nant circuit with the capacitive load, which causes
peaking in the frequency response and degrades the
amplifier’s phase margin.
MAX4028/MAX4029
Triple/Quad, 2:1 Video
Multiplexer-Amplifiers with Input Clamps
_______________________________________________________________________________________ 9
Table 2. MAX4029 Clamp Settings for Video Formats
INPUT FORMAT CLAMP/KEY
1 Cvbs1 Clamp
2 Cvbs2 Clamp
3 Cvbs3 Clamp
4 Cvbs4 Clamp
Gs, B, R have sync only on Green.
INPUT FORMAT CLAMP/KEY
1 H-Sync Clamp
2 G Key
3 B Key
4 R Key
R, G, B have sync on none.
INPUT FORMAT CLAMP/KEY
1 Y Clamp
2 C Key
3 Cvbs Clamp
4 Cvbs Clamp
R, G, B have sync on all.
R
T
75Ω
R
T
75Ω
R
T
75Ω
OUT_
IN_A
IN_B
A/B DISABLE
0.1µF
75Ω CABLE
75Ω CABLE
R
T
75Ω
0.1µF
75Ω CABLE
R
KEYREF
MAX4028
MAX4029
CLAMP
Figure 3. Video Line Driver
INPUT FORMAT CLAMP/KEY
1 Gs Clamp
2 R Key
3 B Key
4 Cvbs Clamp
INPUT FORMAT CLAMP/KEY
1 Y Clamp
2 Pr Key
3 Pb Key
4 Cvbs Clamp
INPUT FORMAT CLAMP/KEY
1 Cvbs Clamp
2G’ Clamp
3B’ Clamp
4R’ Clamp