Rotary Encoder Debounce Circuit


Quantity Pricing

The following are the unit prices, as you vary the quantity purchased:






All prices are in Canadian dollars. We use the total number purchased (ELM401P + ELM401SM) for the calculation.


The ELM401 is an 8 pin integrated circuit that is used to ‘debounce’ the signals from a mechanical rotary (quadrature) encoder. 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 ELM401, as this is all performed within the integrated circuit. The ‘A’ and ‘B’ motion sensing encoder signals are both passed through a filter then a comparator circuit, and finally a timer circuit to remove noise and contact bounce, while the switch input receives standard debounce processing. The result are three virtually noise-free signals that are suitable for direct use by an electronic circuit.

Note that no inversion or manipulation of any kind is performed on the input signals, other than the debouncing. If your applications requires decoding of the signals, you may wish to look at our ELM402 to ELM408 family of products.


  • Microcontroller Interfaces
  • Monitoring of Encoder Signals
  • General Switch Debouncing


  • Low power CMOS design
  • Wide supply range – 2.0 to 5.5 volts
  • Complete debouncing of the encoder signals
  • No external filtering needed
  • Includes switch debouncing circuit
  • Startup delay timer
  • High current drive outputs

Connection Diagram

( PDIP or SOIC, top view )
ELM401 connection diagram

Block Diagram

ELM401 block diagram


The ELM401 data sheet (ver B, 46K):

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