The PHY is responsible for converting information from the data link layer into electrical signals to send and receive across the physical network cabling. The PHY of the Ethernet IEEE 802.3 standard stipulates signalling speeds, network topologies, and electric signal specifications. In this context, the signals transmitted and received across the network will encounter high levels of electrical noise generated by a variety of switch-gear, production equipment, and electric motors. High voltage and high current surges produce radiated and conducted electromagnetic interference in the form of spikes and transients. In large production facilities, with long cable runs (perhaps up to 100 metres),
and equipment producing electromagnetic emissions, such unwanted interference is likely to become induced on the network cables. All equipment connected to the network needs a high degree of electromagnetic immunity (EMI) designed in. Another electrical disturbance comes from electrostatic discharges (ESD). ESD can occur during installation or maintenance of equipment but is also prevalent in production environments with fast-moving materials such as conveyor belts and other production lines. The likelihood of these electrical conditions occurring with an office or data-centre environment is low. However, when designing industrial systems, there is a need for extra precautions to
mitigate the effects of EMC/ESD.
Equipment designed for industrial applications must comply with several internationally recognised EMC and ESD standards, and meet the practical needs of the environment in which it’s installed. The standards referred to include the following EN and IEC standards: 61000-4-5 (surges), 61000-4-4 (electrical fast transients), 61000-4-2 (ESD), and 61000-4-6 (conducted immunity). Also, not only should the equipment be protected from EMI/ESD, but it must also not produce any interference emissions from itself. This requirement is covered by standard EN/IEC 55032 for radiated and conducted emissions compatibility (EMC). For the equipment manufacturer, certification against the standards listed above is a time-consuming and costly process. Selecting components that already comply with the EMC/ESD standards can save considerable amounts of time and speed getting the new product to market.
Another aspect of PHY design and operation is thermal management. As network speeds increase, especially with Gigabit data rates becoming the norm, the amount of supporting circuitry increases too. Factory floor space is always at a premium, with the minimum amount of space available for control cabinets. These cabinets are themselves under pressure to squeeze more and more functions into a limited area, increasing the need for low power consumption, high energy efficiency applications. Equipment mounted closer to the machinery also requires thermal design considerations. Encapsulating or sealing inside a water-resistant enclosure places several design constraints in the way heat can be dissipated while maintaining intrinsic protection against fluids and dust. Again, components that
have energy efficient and low power characteristics simplifies both the mechanical and the electronics design tasks considerably. Most PHYs used in consumer and office equipment have an operating temperature range of 0 ° C to + 70 ° C. Within a space-constrained design, the ambient temperature may well exceed this. The specification for an industrial Ethernet PHY should, therefore, meet the industrial temperature range of -40 °C to + 105 °C.