Encoders and decoders are critical components in many digital systems and applications. They are responsible for converting signals and data between different formats, enabling communication and control. This article provides an overview of encoder and decoder integrated circuits (ICs), their key features, applications and selection considerations.

What are Encoders and Decoders?

Encoders

Encoders are devices that convert information from one format or code to another. The most common types of encoders:

• Optical encoders – Convert linear or rotary motion into digital pulses. Used for position and speed sensing.
• Magnetic encoders – Similar to optical encoders but detect magnetic fields instead of light. More robust against dirt, oils, etc.
• Absolute encoders – Output a unique digital code for each position or shaft angle. Don’t lose position with power loss.
• Incremental encoders – Output digital pulses that indicate incremental motion. Must keep track of position.
• Analog-to-Digital (A/D) encoders – Convert continuous analog signals to digital data. Used in data acquisition.
• Digital encoders – Convert parallel data to serial data or voltage levels and protocols like RS-232.

Decoders

Decoders work in the opposite way of encoders, converting coded inputs into outputs in another format or code:

• Optical decoders – Convert encoded light patterns into outputs. Used in remote controls, etc.
• Digital-to-Analog (D/A) decoders – Convert digital input to an analog output signal. Used in audio, waveform generation, etc.
• Serial-to-Parallel decoders – Convert serial data into parallel data. Used in data communications.
• Decoders/demultiplexers – Convert coded inputs to activate one of many outputs. Used in memory and control logic.

Key Parameters and Specifications

There are several key parameters and specifications to consider when selecting encoder and decoder ICs:

Resolution

The number of discrete steps or positions that can be detected or encoded. Higher resolution provides more precision.

Accuracy

How closely the encoder or decoder matches the actual input or output. Expressed as +/- counts of least significant bit (LSB).

Linearity

How consistent the input to output ratio is across full range. Expressed as nonlinearity as a +/- percentage of full scale.

Repeatability

Ability of encoder to produce same output code for a given position when approached from different directions.

Propagation Delay

Time delay for encoder or decoder to produce output after receiving input. Important for synchronous systems.

Bandwidth/Frequency Response

Maximum operating frequency. Determines response speed of the encoder/decoder.

Operating Temperature Range

Temperature range over which encoder/decoder meets all specifications. Wider range provides application flexibility.

Supply Voltage Range

Range of voltage supplies compatible with the IC. Wider range gives more power supply options.

Package Type

Package size, pin configurations, etc. SMD packages are smaller. Through-hole allows easier prototyping.

Key Encoder/Decoder Applications

Motion Sensing and Control

Incremental encoders paired with motor drives provide speed control and position sensing for motors, robots, and machinery. Absolute encoders provide positional feedback for closed loop motion control.

Analog and Digital Signal Conversion

A/D and D/A encoder/decoder ICs convert between analog signals like audio, video, temperature and digital data for processing, storage and transmission.

Serial Communications

Digital encoders convert parallel data from CPUs to serialized data to transmit over networks. Serial decoders recover the parallel data for use. Used in Ethernet, USB, RS-232/485, etc.

Remote Controls

Optical and RF encoders encode commands from buttons presses on remotes. Decoders recover the commands to control TVs, toys, drones, etc.

Consumer Electronics

Rotary optical encoders detect clicks, scrolling and menu navigation on electronics like MP3 players, digital cameras, etc.

Industrial Sensing

Magnetic and optical encoders provide precision sensing of position, speed, etc. even in dirty factory environments. Used for process control feedback.

Audio and Video Gear

Encoders and decoders enable digital audio and video transmission over fiber optic, coaxial cable, Ethernet in recording studios, etc.

Selecting the Right Encoder or Decoder IC

Here are some tips on selecting the best encoder or decoder IC for your application:

• Match the resolution, accuracy, bandwidth, and operating temperature range to your requirements
• Ensure the power supply voltage range is compatible with your system
• Choose through hole, surface mount or specialized packages as appropriate
• For motion control, incremental encoders offer simplicity, while absolute provides better control
• Optical encoders work well in most factory conditions. Magnetic versions excel in very dirty environments
• SPI and I2C digital encoders simplify communications over short distances
• RS-232, RS-485, and CAN encoder/decoder ICs work well for long range industrial networks
• Audio codecs handle digital audio signals. Video codecs optimized for video compression
• Prefer encoders/decoders with integrated interpolation filters for smoother outputs
• Select devices with robust noise immunity, built-in fault detection and reporting
• Use development kits to evaluate options before fully designing in a specific IC

With the right encoder/decoder IC selected for your requirements, you can efficiently implement robust position, motion, communications and signal conversion in your system. Leverage the parameters and features above along with manufacturer selection tools to choose the optimal solution.

Examples of Popular Encoder and Decoder ICs

Here are some examples of widely-used encoder and decoder integrated circuits:

Key Manufacturers

Some of the leading manufacturers of encoder and decoder ICs include:

• Analog Devices – Broad portfolio of data converters, digital isolators, audio codecs, RS-485 transceivers and more.
• Maxim Integrated – Interface ICs including RS-232, RS-485, SPI, automotive networks, video codecs and drivers.
• Texas Instruments – Audio and video converters and CODECs, interface and driver ICs, SPI, I2C, CAN, LIN.
• NXP Semiconductors – Extensive range including quadrature decoders, RS-485, CAN, LIN, audio/voice codecs, and microcontrollers with built-in encoders.
• STMicroelectronics – MEMS-based motion sensor chips, motor control ICs, audio codecs, high-speed digital codecs and transceivers.
• Infineon – Magnetic encoders, protected RS-485 transceivers, automotive network ICs, security encoder/decoders.
• Microchip – MCUs with hardware encoders/decoders, encoder driver ICs, audio converters and codecs.
• Renesas – Magnetic rotary position sensors, RS-232/485 transceivers, isolation ICs, low-power audio codecs.

These leading vendors offer products for demanding applications across industrial, automotive, audio, video, communications, consumer electronics and more. They provide design resources like selection guides, development kits and simulation models to ease the path from design to production.

Conclusion

Encoders and decoders are essential for converting signals and data between different interfaces, formats and protocols. Selecting the right integrated circuit encoder or decoder solution requires matching specifications like resolution and bandwidth to system requirements. Leading manufacturers offer a diverse portfolio of ICs optimized for motion control, serial communications, audio and video processing, isolation and other applications. By leveraging the latest encoder and decoder ICs, engineers can implement robust and reliable signal and data conversion in their systems.

Frequently Asked Questions

What are the main differences between incremental and absolute optical encoders?

Incremental encoders output digital pulses indicating motion, so systems need to track position and can lose position on power loss. Absolute optical encoders use coded tracks to provide a unique digital word for each position. This allows immediate position readout without losing position on power down.

How do magnetic rotary encoders differ from optical types?

Magnetic encoders use magnetized rings and magnetic sensors to detect the angle and motion of a shaft. They are more resistant to contaminants like dirt, oil, and moisture than optical encoders, but often have lower resolution and higher cost.

When should RS-232 versus RS-485 be used for serial communications?

RS-232 uses single-ended signaling suited for short distances up to 15-20 meters. RS-485 uses differential signaling that minimizes noise and can communicate much further – up to 1200 meters. RS-485 also supports multi-drop networks of many devices using one serial link.

What interface options are available for connecting incremental encoders?

Common digital incremental encoder interfaces include single channel pulse outputs, dual-channel quadrature outputs, as well as serial communications like SPI, BiSS, and SSI which output multiple data bits per reading.

What are the main components of a motion control feedback system?

A motion control feedback system consists of a motor driver, an incremental or absolute encoder to sense position/speed, and a controller that closes the loop by reading the encoder and controlling the motor driver accordingly.