ELM304 データシートの表示（PDF） - Elm Electronics
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ELM304 Datasheet PDF : 6 Pages
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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 3.579545 MHz NTSC television colourburst
crystal is connected between these two pins.
Crystal loading capacitors (typically about 27pF)
will also normally be connected between each of
these pins and Vss.
This frequency was chosen as the crystal should
be readily available, and inexpensive. This circuit
is not able to use the crystal output to generate
colour bars.
Mode (pin 4)
The ELM304 can be selected to operate in one of
two modes depending on the logic level at this
pin. When at a high level, the generated raster
will be 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/gray levels.
V1, V2, and V3 (pins 7, 6, and 5)
These are the digital to analog converter’s logic
level output signals. When combined through a
few appropriate resistors (shown in the Example
Application section), a standard 1Vp-p NTSC
video signal is created. Output levels during the
signal phases are as follows:
Signal Phase
V1
V2
V3
Sync
L
L
L
Blanking
H
L
L
20% White
L
L
H
40% White
H
H
L
60% White
H
L
H
100% White
H
H
H
These signal levels and how they relate to the
actual video waveforms are shown pictorially in
the Example Applications section.
VSS (pin 8)
Circuit common is connected to this pin. This
should be 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 208 mil SOIC surface
mount type of package. To order, add the appropriate suffix to the part number:
300 mil Plastic DIP............................... ELM304P
208 mil SOIC..................................... ELM304SM
All rights reserved. Copyright1999 and 2009 by Elm Electronics Inc.
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.
ELM304DSC
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