“Since its inception, Ethernet has grown by leaps and bounds and is now widely used in commercial and enterprise markets. Due to its well-defined standards and ease of deployment, the widespread spread of Ethernet in the industrial world is also logical. However, it still takes a lot of insight and effort to meet the requirements of Ethernet in harsh industrial environments.
Since its inception, Ethernet has grown by leaps and bounds and is now widely used in commercial and enterprise markets. Due to its well-defined standards and ease of deployment, the widespread spread of Ethernet in the industrial world is also logical. However, it still takes a lot of insight and effort to meet the requirements of Ethernet in harsh industrial environments.
As shown in Figure 1, industrial and commercial environments are quite different and present their own set of challenges. Industrial environments tend to include many harsh conditions, such as higher temperature ranges and voltages, greater noise, mechanical stress, and more. Industrial Ethernet physical layer (PHY) must comply with the requirements of the Ethernet protocol. In this article, I will briefly describe the three most important factors to consider when choosing an Ethernet physical layer for your system.
Figure 1: Modern industrial setup via wireless and wired connections (including Ethernet)
1. Low latency. Latency refers to the time it takes for a packet to travel from source to destination. Different parts of the network will contribute to the total network latency. Communication in industrial networks is time-critical, which means lowest latency and highest determinism. Higher latency and different packet arrival times can degrade system performance.
Standard Ethernet is non-deterministic. The IEEE 802.3 standard does not specify the maximum number of delays for the Ethernet physical layer. However, it becomes very important for Ethernet transceivers in industrial environments to have low and deterministic latency. Low, deterministic latency speeds response time and improves predictability. Low latency allows applications to run faster because information travels through the network with less latency, while high deterministic latency improves synchronization across networks by keeping latency constant.
2. EMI/EMC reduction. Electromagnetic interference (EMI) is electromagnetic energy that is unintentionally generated by a system. Electromagnetic compatibility (EMC), on the other hand, refers to the ability of a system to operate in an environment where other systems generate electromagnetic energy. Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) are important parameters in industrial environments because of the potential for multiple sources of electromagnetic energy. Systems with poor immunity to EMI radiate large amounts of energy, which can disrupt nearby sensitive devices and reduce efficiency because energy is wasted in radiation. A design with poor electromagnetic compatibility can make the system highly sensitive and cause performance problems. The performance of systems with poor EMC design can be affected by other typical sources of radiation, such as Wi-Fi, cell phones, etc.
Different EMI/EMC standards exist, such as European Committee for Standardization (EN), International Special Committee on Radio Interference (CISPR), Federal Communications Commission (FCC), etc., which vary by region and intended market. Devices must meet the requirements specified in these standards before they can be certified for use. These standards vary with the end application of the device. EMI/EMC standards in the industrial market are more stringent than in the commercial market.
3.ESD protection. Electrostatic discharge (ESD) is an electrical current that suddenly enters a system through contact with a charged body. ESD events are short-lived, but they can inject a lot of energy into a system. If the device is not designed to withstand such an event, the result is likely to be devastating for the device, often resulting in its destruction. Since electrostatic discharge does not always leave visible signs of damage, it can be difficult to find damaged equipment in complex systems. As such an important parameter, ESD standards have been formulated so that devices must meet their minimum requirements, such as International Electrotechnical Commission (IEC) 61000-4-2, depending on their end application. Similar to EMI/EMC, ESD requirements in the industrial market are more stringent than in the commercial market.
Industrial Ethernet PHYs should have low deterministic latency, meet stringent EMI/EMC standards, and be resistant to ESD events. TI’s Ethernet portfolio is designed to meet these requirements and is already in use in many harsh industrial environments around the world, including the DP83867 Gigabit Ethernet PHY customized for harsh industrial environments and the DP83826E low latency 10/100Mbps Ethernet Physical layer and other equipment.