MAX11501 Datasheet, PDF (6/11 Pages) Maxim Integrated Products – Three-Channel, Standard-Definition Video Filters

Three-Channel,
Standard-Definition Video Filters
2.32V
MAX11501
MAX11502
OUTPUT SIGNAL
1.02V
IN_
OUT_
0.92V
INPUT SIGNAL
0.32V
0.32V
0.02V
0.00V
Figure 2. Typical DC-Coupled Signal
Input Coupling
The choice of AC- or DC-coupling the input depends
on the video source. Many DACs provide a current out-
put and are terminated to ground with a resistor. Such
DAC outputs are conveniently DC-coupled to the
MAX11501/MAX11502. Use AC-coupling when the DC
level of the video signal is unknown or outside the
specified input range of the MAX11501/MAX11502,
such as SCART or V_CC terminated 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).
ENCODER
DAC
MAX11501
0.1μF
MAX11502
IN_
Figure 3. Simple AC-Coupling for Unipolar Signals (Y, R, G, B)
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 pulses (Figure 3).
For bipolar signals such as Pb and Pr, bias the AC-cou-
pled inputs to a fixed DC voltage, typically 0.59V, to ensure
that the transparent clamp remains off. A suitable network
is shown in Figure 4. Determine the bias voltage using:
ENCODER
DAC
0.1μF
V_CC
R1
820kΩ
R2
120kΩ
MAX11501
MAX11502
IN_
( ) ^VB
=
R2
R1 + R2
×
V_CC − ₍I_L × R1₎ ,
where I_L is the input leakage current (typically 0.5µA).
Figure 4. AC-Coupling for Bipolar Signals (Pb, Pr)
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