CLC3801ISO8X datasheet(12/17 Pages) CADEKA

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Data Sheet

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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.

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,

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.

Figure 2. Typical DC-coupled Signal for CLC3800

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 VIN range is generally limited by the output. VIN

and VOUT 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”.

0.00V

0.02V

Input Signal

0.32V

1.02V

0.35V

Output Signal

0.97V

2.39V

CLC3800

IN1

OUT1

IN2

IN3

OUT3

+Vs

OUT2

GND

Video

DAC/

Encoder

R or Y

B or PR

G or PB

DAC Load Resistors

per Video DAC/Encoder specs

+3V or +5V

0.1µF

1.0µF

CLC3801ISO8X Datasheet(PDF) 12 Page - Cadeka Microcircuits LLC.

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