Skip to main content

Multiplexer (MUX) and Demultiplexer (DEMUX) Applications

Published Date
Author Cadence PCB Solutions

Key Takeaways

  • A multiplexer is also called a data selector, as it utilizes ‘SELECT’ inputs to route the desired data input to the output.

  • Multiplexers can easily replace logic gates and implement logic with the advantage of changing the function whenever required.

  • Multiplexer and demultiplexer applications are present in data acquisition systems, sensor arrays, multi-channel systems, etc.

       MUX and DEMUX

MUX and DEMUX

Multiplexers and demultiplexers are used to reduce complexity in wireless systems, satellite applications, space communication, and high-speed optical circuits. Multiplexer (MUX) and demultiplexer (DEMUX) applications include digital systems, computer networks, and communication systems.

In most cases, if a multiplexer is used, a demultiplexer is also used in conjunction to separate signals. Multiplexer and demultiplexer applications reduce the cost, space, and power requirements in electronic circuits.   

System Optimization With Multiplexers and Demultiplexers

Feature

Multiplexer

Demultiplexer

Cost 

Saving

In applications where a single device needs to process multiple input signals, a multiplexer can be used to select and route the signals to a common processing unit. With the inclusion of multiplexers, the cost of incorporating multiple processing units can be avoided.

Whenever a single data needs to be transmitted to multiple devices, demultiplexers can send it to the intended devices. Demultiplexers enable the transmission of data to different output channels such as video, audio, etc. With demultiplexers, hardware duplication is avoided, saving money in the process. 

Space

Saving

Multiplexers allow the distribution of signals via a single device or single transmission line. The count of lines or devices is reduced with the help of multiplexers, optimizing available space. 

The distribution of a signal to multiple channels with the help of demultiplexers reduces the requirement for multiple input ports in associated devices. The footprint of related devices can be reduced by incorporating demultiplexers. 

Power

Saving

As a multiplexer enables the processing of multiple signals with a single device, power consumption is minimized and power efficiency is improved. 

By eliminating the need for hardware duplication in different output channels, demultiplexers indirectly save power. 

Usually, multiplexer and demultiplexer applications are implemented using semiconductor components – especially CMOS devices or Heterojunction Bipolar Transistors (HBT). Multiplexer (MUX) and demultiplexer (DEMUX) applications requiring low power consumption focus on CMOS-based implementation, whereas high-speed and high-frequency applications are better realized using HBT technology. The sections below give two examples of multiplexer and demultiplexer applications.  

Multiplexer (MUX) and Demultiplexer (DEMUX) Application Examples

Logic circuit

Application

Description

Multiplexer

Logic generator

Replaces the combination of logic gates and implements logic functions with the provision of changing the function easily.

Parallel-to-serial data converter

Enables conversion of parallel data to serial form and transmits over a single output line. 

Demultiplexer

Serial-to-parallel data converter

Serial data is converted to parallel data and distributed to multiple devices.

Single-source to multiple destinations

Data can be sent from a single source to multiple destinations chosen based on the select signal. 

Multiplexers as Logic Generators

Multiplexers can be used to generate logic. Usually, a combination of logic gates is used to realize a Boolean expression consisting of a set of inputs. Multiplexers can easily replace logic gates and implement logic with the advantage of changing the function whenever required. Using a single multiplexer IC, complex logic expressions can be realized.

Consider the function F = A ⊕ B ⊕ C . There are three input variables: A, B, and C, hence the multiplexer selected is of three data select inputs S0, S1, and S2. The three data select inputs make it an 8-to-1 MUX. The function can be implemented using the truth table given below.  

Truth table of the function F = A ⊕ B ⊕ C and implementation using MUX
Truth table of the function F = A ⊕ B ⊕ C and implementation using MUX

From the truth table, it is clear the function equals 1 only when ABC corresponds to 001, 010, 100, and 111.  Therefore the data inputs D1, D2, D4, and D7 are connected to binary 1 and the rest of the data inputs to logic 0. Multiplexers as logic generators are employed in digital circuits used in function generators, arithmetic logic units, control units, digital signal processors, memory systems, I/O interfaces, etc. 

Parallel-to-Serial Data Conversion With Multiplexers

Parallel data can be converted to serial data using a multiplexer circuit. The multiplexer and counter enable parallel to serial data conversion. The output of the counter is connected to the select inputs of the multiplexer. The parallel data is applied to the multiplexer inputs sequentially as the counter counts.

When the counter finishes one complete count sequence (say 000 to 111), the parallel data is converted into serial data and is given to the output line. The multiplexer functioning as a parallel-to-serial-data converter is used in UART interfaces, I2C, and SPI protocol-based systems.  

Serial-to-Parallel Data Conversion With Demultiplexers

While a multiplexer performs parallel to serial data conversion, demultiplexers convert serial data to parallel data. There are applications in computer systems or networks requiring serial-to-parallel data conversion, and demultiplexers are employed for the conversion functionality. 

For example, in high-speed serial communication interfaces, say PCIe buses, demultiplexers take the serial bus data as data inputs, split the data into parallel streams, and direct it towards the respective receiving devices such as storage devices, GPU, CPU, etc.  

Single Source to Multiple Destination Applications

Consider sending data from a computer to different devices such as a fax machine, pen plotter, printer, etc. In this application, a demultiplexer can be used to select from multiple destinations. The select signal is used to choose between the various devices. 

Cadence Supports MUX and DEMUX Applications

Multiplexer (MUX) and demultiplexer (DEMUX) applications are present in data acquisition systems, sensor arrays, multi-channel systems, etc. Cadence’s suite of PCB design and analysis tools can help you design digital systems employing multiplexers and demultiplexers.

Leading electronics providers rely on Cadence products to optimize power, space, and energy needs for a wide variety of market applications. If you’re looking to learn more about our innovative solutions, talk to our team of experts or subscribe to our YouTube channel.