ELM304
NTSC Video Generator
Description
The ELM304 is a low-cost NTSC video signal
generator in an 8 pin package. Requiring only an
external crystal and a few passive components, this
circuit produces a stable raster that is suitable for a
variety of video applications.
The ELM304 can be ‘programmed’ to generate
either a solid white raster or a four-level gray scale
pattern simply by changing the logic level at the
mode input pin. A supplied internal pullup resistor
further simplifies the circuitry when interfacing to
mechanical switches.
Although originally designed to provide a stable
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.
Features
• Low power CMOS design - typically 1mA at 5V
• Wide supply range - 3.0 to 5.5 volt operation
• Uses a standard 3.58MHz crystal
• Generates both solid and bar type patterns
• No external amplifier required
• Standard 1V p-p NTSC sync negative output
• Requires no adjustments
Connection Diagram
PDIP and SOIC
(top view)
V
DD
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
XT1
XT2
Mode
Block Diagram
7
V1
V2
V3
XT1
XT2
2
Master
Oscillator
3
Pattern
Generator
Output
Matrix
6
5
V
DD
Mode
4
ELM304DSB
Elm Electronics – Circuits for the Hobbyist
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