ELM401
Pin Descriptions
VDD (pin 1)
Sw out (pin 5)
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 internal logic, so an external
reset signal is not required. Refer to the Electrical
Characteristics section for more information.
This output is the debounced representation of the
signal that is at pin 4.
B out (pin 6)
This output is the debounced representation of the
signal that is at pin 3.
A (pin 2)
A out (pin 7)
This input is usually connected to what is normally
known as the ‘A’ signal from a rotary (quadrature)
encoder. An external pullup resistor is required for
the encoder (a typical value is 10 KW), but no
external capacitors are needed (as the internal
debounce circuitry provides the filtering).
This output is the debounced representation of the
signal that is at pin 2.
VSS (pin 8)
Circuit common is connected to this pin. This is the
most negative point in the circuit.
B (pin 3)
This input is usually connected to what is normally
known as the ‘B’ signal from a rotary (quadrature)
encoder. An external pullup resistor is required for
the encoder (a typical value is 10 KW), but no
external capacitors are needed (as the internal
debounce circuitry provides the filtering).
Sw (pin 4)
This input may be used to debounce any standard
mechanical contact (from a switch or relay). The
circuitry uses simple set/reset logic to control a timer,
so is not suitable for use with the A or B signal from
a rotary encoder (as those signals continue to
generate sliding noise while the contact is closed).
All rights reserved. Copyright 2011 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.
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ELM401DSB
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