Data Sheet
Application Information
Basic Operation
The CLC3800, CLC3801, and CLC3802 are 3-channel video
amplifiers that operate with single supply voltages from
3V to 7V. They are designed to accept DC-coupled inputs
and will drive AC- or DC-coupled outputs. Each channel
integrates a DC offset, 4th order Butterworth filters, and
fixed gain video drivers. The filtering is appropriate for
standard definition video signals and has a -3dB cutoff
of 8.6MHz. This cutoff provides an excellent compromise
between flat in-band response and high frequency noise
reduction. The input signals are level shifted prior to the
input filters and output amplifiers.
Inputs: DC-Coupled
The inputs must be DC-coupled. Many DACs provide a
current output that is resistively terminated to ground.
These DACs are conveniently DC-coupled to the inputs of
the CLC3800, CLC3801, or CLC3802 as shown in Figure 1.
DC-coupled inputs use fewer components and lowers the
overall system cost.
raising the input signal by approximately 330mV. For
example, when 0V is applied to the input, the output
becomes approximately 330mV above ground. This offset
eliminates sync tip clipping. Figure 2 illustrates a typical DC-
coupled input signal and resulting output signal after exiting
the CLC3800.
2.39V
C
omlinear
CLC3800, CLC3801
Triple, Standard Definition Video Amplifiers
Output Signal
1.02V
0.97V
Input Signal
0.35V
0.32V
0.02V
0.00V
Figure 2. Typical DC-coupled Signal for CLC3800
DAC Load Resistors
per Video DAC/Encoder specs
R or Y
1
IN1
OUT1
8
Video
DAC/
Encoder
G or P
B
2
IN2
OUT2
7
The input voltage range is typically 0V to 1.4V for the
CLC3800 at 5V supply. Due to the internal fixed gain of 6dB
(for the CLC3800) and the internal level shift of nominally
330mV, the V
IN
range is generally limited by the output. V
IN
and V
OUT
are fully detailed in the Electrical Characteristics
section.
Outputs: AC- or DC-Coupled
Each channel of the CLC3800, CLC3801, and CLC3802 can
drive either AC- or DC-coupled loads. Each channel can
drive single or dual video loads, 150Ω (1 video load) or 75Ω
(2 video loads). Figure 3 shows the typical configuration
for driving either AC- or DC-coupled loads.
With DC-coupled loads, AC-coupling capacitors are not
used. Match the series termination resistors to the typical
cable impedance, 75Ω for standard video cable. Keep the
output connection to the series termination resistors as
short as possible. If driving 2 video loads, place both
resistors close to the CLC3800.
With AC-coupled loads, use an AC-coupling capacitor
of at least 220μF in a 75Ω environment. A value of at
least 220μF will ensure that low frequencies are passed,
preventing video droop across the line, referred to as “tilt”.
CLC3800
B or P
R
3
IN3
OUT3
6
+3V or +5V
4
+Vs
GND
5
1.0µF
0.1µF
Figure 1. Typical Input Configuration
The input termination/source resistance is set by the
application. Any value up to several kΩ can be used. Lower
values reduce noise, but if higher values are needed, there
is little effect on filter shape or distortion performance of
the CLC380x. If the CLC380x is located on the same board
as the video source, and within a few inches, the input
termination resistance is determined by the requirements
of the Video DAC or Encoder. If a cable is needed to
connect the CLC380x to the video source, the termination
must match the cable impedance which is 75Ω for standard
video cable.
The CLC380x Family of video amplifiers add a DC offset,
©2008-2010 CADEKA Microcircuits LLC
Rev 1C
www.cadeka.com
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