ELM304
NTSC Video Generator
Description
The ELM304 is a low-cost NTSC video signal
generator in an 8 pin package. It requires only a few
external components in order to generate a stable
monochrome raster that is useful in a variety of
video applications.
The ELM304 can generate either a solid white
raster or a four-level gray scale pattern simply by
changing the logic level at the Mode input pin. An
internal pullup resistor simplifies the connection of
this pin to mechanical switches.
Although originally designed to provide a video
input signal for use while recording audio on video
cassette recorders, this circuit can also be used for
many other instructional and test purposes. The low
power consumption and small size of the circuit also
makes it ideal for battery-powered applications.
Please note that while this circuit uses a colour-
burst crystal as a timing reference, the ELM304 will
not actually generate a colourburst, so the output is
monochrome (ie ‘Black and White’).
Features
• North American 525 line 60Hz NTSC signal
• Standard 1V p-p NTSC sync negative output
• Generates both solid and bar type patterns
• No external amplifier required
• Requires no adjustments
• Wide supply range - 3.0 to 5.5 volt operation
• Uses a standard 3.58MHz crystal
• Low power CMOS design
Connection Diagram
PDIP and SOIC
(top view)
V
DD
XT1
1
2
3
4
8
7
6
5
V
SS
V1
V2
V3
Applications
• Video Source for Video Cassette Recorders
• Classroom Instructional Aid
• Test Bench Video Generator
XT2
Mode
Block Diagram
7
V1
V2
V3
XT1
XT2
2
Master
Oscillator
3
Pattern
Generator
Output
Matrix
6
5
V
DD
Mode
4
ELM304DSC
Elm Electronics – Circuits for the Hobbyist
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