SEMICONDUCTORS
Evaluation board description
This evaluation board has been developed to allow the
user to quickly evaluate the ZXFV4583 Sync separator
IC and the ZXFV4089 dc restoration video amplifier.
The evaluation board schematic diagram is shown in
Figure 1, and the printed circuit layout is shown in
Figures 2, 3 and 4.
The analog video source is brought onto the board via
a BNC connector socket and is terminated via a 51⍀
resistor. This provides matching to standard
laboratory test instruments. The circuit can be easily
adapted for 75⍀ source impedance by changing
resistor R1.
The incoming video signal is ac coupled to the
ZXFV4583 via capacitor C1 and is ac coupled to the
ZXFV4089 by capacitor C7.
HeaderPL2inconjunction withlinks LK1and LK2allow
the incoming video signal to be passed through the
internal color burst filter or to bypass it.
To use the color burst filter:
Links LK1 should be connected between PL2:1 and PL2:6
LinkLK2shouldbeconnectedbetweenPL2:4andPL2:5
To bypass the color burst filter:
Links LK1 should be connected between PL2:2 and PL2:5
LinkLK2shouldbeconnectedbetweenPL2:3andPL2:4
TestpointTP2 hasbeenprovidedtomonitor theoutput
of the color burst filter.
Diagrams of this are shown on the PCB itself.
The synchronized logic outputs of the ZXFV4583 are
brought to header H1 for examination using
oscilloscope probes
The ZXFV4089 DC Restoration Amplifier, which is
described in its own datasheet, uses the Back Porch
output from the ZXFV4583 in order to control and
stabilize the black level of a video waveform.
The ZXFV4089 contains an uncommitted current
feedback amplifier. This evaluation board uses
resistors R7 andR8 to set the gain ofthis amplifier. The
default gain setting of the evaluation board is +2 or
6.02dB.
The output circuit includes a resistor matching circuit
to present a load of 150⍀ to the amplifier while
simultaneously providing a 50⍀ output impedance to
any test instrument connected to the BNC connector.
Theattenuationofthismatchingcircuit is19.92dB.This
results in an overall gain for a 50⍀ system of:
6.02 - 19.92 = -13.9dB.
PCB design
A continuous ground plane is required under the
device and its signal connection paths, to provide the
shortest possible ground return paths for signals and
power supply filtering.
A double-sided or multi-layer PCB construction is
required, with plated-through via holes providing
closelyspaced low-inductanceconnectionsfrom some
components to the continuous ground plane.
Power supply filtering
For the power supply filtering, low inductance surface
mount capacitors are normally required. It has been
found that very good RF decoupling is provided on
each supply using a 1000pF NPO size 0805 or smaller
ceramic surface mount capacitor, closest to the device
pin, with an adjacent 0.1F X7R capacitor. However
larger decoupling capacitors elsewhere on the printed
circuit board, values of 1 to 10F, are also
recommended, particularly where the voltage
regulators are located morethan a few inches from the
device. These larger capacitors are recommended to
be solid tantalum electrolytic or ceramic types
.
ZXFV4583EV
ISSUE 1 - MAY 2004
SYNC SEPARATOR AND DC RESTORATION AMPLIFIER
EVALUATION BOARD
1
