ELM402
Rotary Decoder - 2 wire 2x Interface
Description
Features
The ELM402 is an 8 pin integrated circuit that is
• Low power CMOS design
• Wide supply range – 2.0 to 5.5 volts
• Complete debouncing of the encoder inputs
• No external filtering needed
• 2x decoding
used to convert the signals from a rotary encoder
into a series of up and down output pulses. The low
power CMOS technology used ensures that only a
very small current is required over the entire 2.0 to
5.5 volt operating range.
There is no need for external filtering or
debounce circuits with the ELM402, as this is all
performed within the integrated circuit. After
debouncing the encoder signals, the ELM402 then
determines the direction of shaft rotation, and
generates the appropriate pulses at the Up or Down
output pins. The duration of these pulses can be
selected for either 0.2 or 2.0 msec.
• Startup delay timer
• High current drive outputs
Connection Diagram
PDIP and SOIC
(top view)
The ELM402 provides 2x decoding of a rotary
encoder signal. If your application requires 4x
decoding, please see the ELM403 (it is identical to
the ELM402 in every respect, except that it provides
4x decoding).
1
2
3
4
8
7
6
5
VDD
A
VSS
Up
Applications
B
Down
• Digital audio potentiometer controls
• Variable voltage or temperature circuits
• Positioning controls
Pulse
Width
Output
Invert
• Tuning circuits
Block Diagram
VDD
A
Debounce
Circuit
2
7
Up
Direction
Decoding
Output
Logic
VDD
B
Debounce
3
6
Down
Circuit
Rotary
Encoder
4
5
Pulse
Width
Output
Invert
ELM402DSA
Elm Electronics – Circuits for the Hobbyist
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