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
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
VSS (pin 8)
Circuit common is connected to this pin. This is
the most negative point in the circuit.
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.
Elm Electronics – Circuits for the Hobbyist
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