Protecting Wired Communication in IoT

This is the first article in a 7-part series examining circuit protection. The series examines the challenges of high-speed circuit protection, as well as the many products and solutions used to solve them. This series is sponsored by Mouser Electronics, an online distributor of electronic components. Through their sponsorship, Mouser Electronics shares its passion for technologies that enable a safe and connected world.

Standards enable wired communication 

Over the last decade, electronic solution advances have enabled wireless communication to flourish and given rise to the Internet of Things (IoT). Despite the abundance of breakthroughs in wireless communication, a large portion of today’s communication is handled by wired communication with applications that include telephone networks, cable television, internet access, and fiber-optic communication. These complex systems are made up of a huge range of communication standards that have been developed for each specific application. With each standard and application comes a unique set of challenges to protect them. This article briefly introduces these standards and how to protect them, future articles in the series will outline in more depth how to design to mitigate risk in wired IoT communication. 

Wired Communication Standards

Automotive

Electronics components are being increasingly integrated into vehicles, enabling connections to the IoT world. Prominent approaches to high-speed serial interfaces in this industry include Controller Area Network (CAN) bus and Local Interconnect Network (LIN) bus. CAN is a robust bus standard utilized in transportation applications. It is designed to allow microcontrollers (MCUs) and related components to communicate with each other’s applications. This is done without requiring that the system have a host computer. 

Figure 1: A CAN Bus example. 

LIN is a low-cost serial network protocol. It is employed to send data between various electronic solutions inside vehicles. It is intended to complement the CAN network as part of a hierarchical network within transportation. LIN supports up to 16 devices, connected to the same communication wire, along with a bus protocol that arranges data bytes for coherent transmission to microcontrollers for further processing. Using only one wire for 16 devices keeps build and material costs contained while adding smart technology to cars.

Figure 2: LIN versus CAN window control. 

LIN nodes are typically bundled in clusters, each with a master that interfaces with the backbone CAN bus. Example above: In a car's right seat you can roll down the left seat window. To do so, you press a button to send a message via one LIN cluster to another LIN cluster via the CAN bus. This triggers the second LIN cluster to roll down the left seat window

Solutions to protect automotive systems include AEC-Q101/Q200- qualified transient-voltage-suppression (TVS) diodes and varistors where the electrical resistance varies with applied voltage. Additionally, resettable fuses are fast becoming the industry standard. 

Portable & Consumer Devices

Universal Serial Bus (USB) is an industry-standard that establishes specifications for cables and connectors and protocols for connection, communication, and power supply between computers, peripherals, and other computers. It is the connector, charger, and power supply for a host of portable and consumer devices such as mobile phones, smartwatches, and wearables. One of today’s standard USB interfaces is Type C. It enables devices to transmit both power and data on a single cable in a standardized industry method. Type C USB is replacing previous standards such as lightning and micro USB and becoming an industry standard across brands. 

High-speed USB protection comes by delivering power and signals protection through an assortment of TVS diodes, and resettable positive temperature coefficients (PPTC) fuse devices. 

Figure 3: Type C connector.

Industrial & Data Center

This is a disparate and extensive application sector that includes energy production, storage, and distribution, construction and development, mining and resource extraction as well as data storage and management. 

Industrial and data center applications are often interfaced with RS-485, Ethernet, and Power Over Ethernet (PoE). RS-485 is a standard balanced interconnecting cable and network topology. It provides the opportunity for interfaces to be point-to-point, multi-dropped, and multi-point. The standard has wide application possibilities from being used in lighting systems in theatre and performance venues, to building automation systems to Digital Command Control (DCC) for model railways.  

Figure 4: A schematic of a PoE System. 

Ethernet is a way to connect computers into a localized cluster known as a local area network (LAN) or wide area network (WAN). Power over Ethernet (PoE, PoE+, and PoE++) builds upon Ethernet. It enables an Ethernet system to pass electric power along with data. 

PoE allows network installers to deploy powered devices in locations that lack electrical wiring. This eliminates the expense of installing additional wires, which would otherwise need professional installation by experienced electricians familiar with strict regulations regarding conduit usage. 

Protective measures include RS-485 solutions that offer signal and power protections utilizing PTCs and TVS diodes. Fuses, Gas Discharge Tubes (GDTs), and TVS diodes safeguard power and signals where Ethernet is employed

Summary

In the first article of this series, we have outlined the different wired communication standards for common applications including automotive, portable & consumer devices, and industrial & data centers.  Future articles will go into deeper detail about the specific kinds of blockade protection for each standard. 

This article was initially published by Mouser and Littlefuse in an e-magazine. It has been substantially edited by the Wevolver team and electrical engineer Fahad Farooq. It's the first article of a 7-part series examining circuit protection.  Future articles provide an overview of how to protect wired communication, the change of USB standards, and the importance of protecting against electrical stress in industrial automation environments.

About the sponsor: Mouser Electronics

Mouser Electronics is a worldwide leading authorized distributor of semiconductors and electronic components for over 1,100 manufacturer brands. They specialize in the rapid introduction of new products and technologies for design engineers and buyers. Their extensive product offering includes semiconductors, interconnects, passives, and electromechanical components.