MAX11504/MAX11505
Transparent Clamps
All inputs feature transparent clamps that allow either
AC or DC input coupling. The clamp remains inactive
while the input signal is above ground, offering true DC
input coupling. If the signal goes below ground, as
occurs when it is AC-coupled, the clamp sets the sync
tip slightly below the ground level.
Input Coupling
The choice of AC- or DC-coupling the input depends
on the video source. Many DACs provide a current
output and are terminated to ground with a resistor;
such signals are conveniently DC-coupled. Use AC-
coupling when the DC level of the video signal is
unknown or outside the specified input range of the
MAX11504/MAX11505, such as SCART or V
CC
-termi-
nated DAC outputs.
DC-Coupled Inputs
If the input is DC-coupled, the input voltage must
remain above zero but not exceed the maximum input
voltage of 1.4V (typical).
AC-Coupled Inputs
If the input is AC-coupled, the transparent clamps are
active and set the lowest point of the signal at ground.
This is appropriate for unipolar signals such as Y, R, G,
or B with or without sync pulse (Figure 3).
Four-Channel, Standard-Definition
Video Filters
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