Since its inception, Ethernet has experienced rapid development and is now widely used in commercial and enterprise markets. Its widespread adoption in the industrial world is also understandable given its well-defined standards and ease of deployment. However, meeting the requirements of Ethernet in harsh industrial environments still requires significant insight and effort.
As shown in Figure 1, industrial environments differ significantly from commercial environments and present a range of challenges. Industrial environments often include harsh conditions such as higher temperature ranges and voltages, higher noise levels, and mechanical stress. Industrial-grade Ethernet physical layers (PHYs) must comply with the requirements of the Ethernet protocol. In this article, I will briefly describe three of the more important factors to consider when selecting an Ethernet physical layer for your system.
1. Low latency. Latency refers to the time it takes for a data packet to travel from its source to its destination. Different parts of the network contribute to the total network latency. Communication in industrial networks has stringent time requirements, meaning that latency should be minimal and deterministic. Higher latency and inconsistent packet arrival times degrade system performance.
Standard Ethernet is inherently non-deterministic. The IEEE 802.3 standard does not specify a maximum latency for the Ethernet physical layer. However, low and deterministic latency becomes crucial for Ethernet transceivers in industrial environments. Low and deterministic latency accelerates response times and improves predictability. Low latency allows applications to run faster because information waits less time to propagate through the network, while deterministic latency improves synchronization between different networks due to its constant latency.
2. EMI/EMC. Electromagnetic interference (EMI) is electromagnetic energy unintentionally generated by a system. Electromagnetic compatibility (EMC), on the other hand, refers to a system's ability to operate in environments where other systems generate electromagnetic energy. EMI and EMC are critical parameters in industrial environments because they can have multiple sources of electromagnetic energy. Systems with poor EMI immunity radiate significant amounts of energy, disrupting nearby sensitive devices and reducing efficiency because energy is wasted in the radiation. Poor EMC design makes the system highly sensitive and leads to performance problems. The performance of systems with poor EMC design is also affected by other typical radiation sources, such as Wi-Fi and mobile phones.
Different EMI/EMC standards exist, such as those of the European Committee for Standardization (EN), the International Special Committee on Radio Interference (CISPR), and the US Federal Communications Commission (FCC). These standards vary depending on the region and the intended market. Equipment must meet the requirements of these standards before it can be certified for use. These standards vary depending on the end application of the equipment. EMI/EMC standards in the industrial market are more stringent than those in the commercial market.
3. ESD Protection. Electrostatic discharge (ESD) is a sudden influx of current into a system upon contact with a charged object. ESD events are brief, but they can inject a significant amount of energy into a system. If a device's design cannot withstand such events, the consequences can be catastrophic, often resulting in device failure. Because ESD does not always leave obvious signs of damage, it can be difficult to locate damaged equipment in complex systems. As such a crucial parameter, standards such as the International Electrotechnical Commission (IEC) 61000-4-2 have been established to set minimum requirements that devices must meet—which devices must meet depends on their end application. Similar to EMI/EMC, ESD requirements in the industrial market are more stringent than those in the commercial market.
Industrial-grade Ethernet physical layers 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 used in many harsh industrial environments around the world, including devices such as the DP83867 Industrial Gigabit Ethernet Physical Layer and the DP83826E10/100 Ethernet Physical Layer.
