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ELM304 Datasheet Preview

ELM304 Datasheet

NTSC Video Generator

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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.
www.DataSheet4UA.clthoomugh 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.
Applications
• Video Source for Video Cassette Recorders
• Classroom Instructional Aid
• Test Bench Video Generator
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)
VDD
XT1
XT2
Mode
1
2
3
4
8 VSS
7 V1
6 V2
5 V3
Block Diagram
XT1 2
XT2 3
Master
Oscillator
Pattern
Generator
Output
Matrix
Mode 4
VDD
7 V1
6 V2
5 V3
ELM304DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
1 of 4




ELM Electronics

ELM304 Datasheet Preview

ELM304 Datasheet

NTSC Video Generator

No Preview Available !

ELM304
Pin Descriptions
VDD (pin 1)
This pin is the positive supply pin, and should
always be the most positive point in the circuit.
Internal circuitry connected to this pin is used to
provide power on reset of the microprocessor, so
an external reset signal is not required. Refer to
the Electrical Characteristics section for further
information.
XT1 (pin 2) and XT2 (pin 3)
A 3.579545MHz NTSC television colourburst
crystal is connected between these two pins.
Crystal loading capacitors (typically 27pF) will
www.DataSheet4aUlso.cnoomrmally be connected between each of the
pins and Vss.
Mode (pin 4)
The ELM304 can be selected to operate in one of
two modes depending on the logic level on this
pin. When at a high level (or open-circuited), the
generated raster is solid white in colour. If this pin
is held at a low level, the circuit will generate a
four-level pattern of typically 100%, 60%, 40%
and 20% white.
V3, V2, and V1 (pins 5, 6, and 7)
These are the digital to analog converter’s logic
level output signals. When combined through a
few appropriate resistors (see the example
application section), a standard 1Vp-p NTSC
video signal is created. Output levels during the
signal phases are as follows:
Signal Phase V3 V2 V1
Sync
LLL
Blanking
LLH
20% White
HL
L
40% White
L HH
60% White
HL
H
100% White
H
H
H
VSS (pin 8)
Circuit common is connected to this pin. This is
the most negative point in the circuit.
Ordering Information
These integrated circuits are available in either the 300 mil plastic DIP format, or in the 200 mil SOIC surface
mount type of package. To order, add the appropriate suffix to the part number:
300 mil Plastic DIP............................... ELM304P
200 mil SOIC..................................... ELM304SM
All rights reserved. Copyright ©1999 Elm Electronics.
Every effort is made to verify the accuracy of information provided in this document, but no representation or warranty can be
given and no liability assumed by Elm Electronics with respect to the accuracy and/or use of any products or information
described in this document. Elm Electronics will not be responsible for any patent infringements arising from the use of these
products or information, and does not authorize or warrant the use of any Elm Electronics product in life support devices and/or
systems. Elm Electronics reserves the right to make changes to the device(s) described in this document in order to improve
reliability, function, or design.
ELM304DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
2 of 4


Part Number ELM304
Description NTSC Video Generator
Maker ELM Electronics
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ELM304 Datasheet PDF






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