Compact, Integrated Connector Modules Cut Noise and Supply Power over Ethernet for AI Applications

With the explosive growth of networked devices, network designers are continually reconsidering the types and volume of data collected by edge nodes, where that data needs to go, and how to best get it there. Increasingly, getting power to those edge nodes also falls onto the network designer’s list.

Power over Ethernet (PoE) is one technology that addresses both data transmission and power. This article will review PoE technology, explore the future of PoE in artificial intelligence (AI) and machine learning (ML) applications, and cover the aspects network designers must consider when selecting PoE components.

How differential signaling enables PoE

Ethernet facilitates a reliable, time-sensitive network of connectivity with inherent noise reduction. Modern Ethernet cables, classified as CAT 5 and CAT 6 types, contain eight wires that form four twisted pairs. Data is sent over each twisted pair in the form of differential voltage signals. When one wire of a twisted pair is pulled up to a positive voltage, the other wire is pulled down to an identical negative voltage. The sign of the resulting differential voltage encodes the data being sent.

Differential signals are inherently immune to certain types of electromagnetic interference (EMI), such as common-mode noise. This is because such interference would raise or lower the transmitted voltage on both wires in the twisted pair by the same amount, resulting in the same ultimate differential voltage. This noise immunity is what initially led to the wide adoption of Ethernet technology and is what makes PoE possible.

In PoE installations, different DC biases are applied to different twisted pairs within a cable without affecting the individual differential voltage signals. A filter circuit separates out the AC data signals to be sent to a controller, while a power circuit draws power from the DC bias.

Ethernet cables, RJ45 jacks, and networking protocols are defined by the IEEE 802.3. That standard further delineates three different power levels for PoE applications while leaving room for higher power levels in the future (Table 1).

Table 1: PoE installations conform to different parts of IEEE 802.3 depending on the power they supply, along with Ethernet connectivity. (Image Source: Bel)

Low-power PoE setups per IEEE 802.3af provide up to 15.4 W for devices like sensors, Internet of Things (IoT) devices, and simple single-board computers. IEEE 802.3at defines medium-power PoE+ setups that provide up to 30.0 W to network routers, monitors, and IoT devices with onboard or edge processing capabilities. The highest level of power is supplied by PoE++ setups, defined by IEEE 803.2bt. These installations provide up to 90.0 W to thin clients, industrial automation systems, LED lighting, and security cameras.

The potential of PoE

Regardless of power level, PoE simplifies and error-proofs installations by eliminating the need for separate power cables, plugs, and AC/DC converters. A single cable also removes many of the possible failure points, simplifying troubleshooting and energy optimization.

The development of PoE standards has paved the way for AI and ML applications. For example, consider a network of low-power sensors connected via Type 1 PoE. Without having to deploy miles of power cables or have power supplies distributed over a large open area, network designers can create a mesh of data that feeds directly to an AI processor, providing real-time knowledge about an environment.

Using Type 2 PoE installations, that AI processing can be distributed at edge nodes. AI and high-compute routines can run locally where data is being collected. This creates a more agile network that can react in real time to its environment while preserving core computing power for other tasks.

Type 3 and 4 PoE installations support the higher-demand computing systems that provide even more robust AI edge processing. The higher power available with Type 4 PoE supports machine vision and other ML processes that can revolutionize industrial automation capabilities.

As the power supplied by a PoE network and the volume of data transmitted increase, concerns over EMI and radio-frequency interference (RFI) grow as well. Expanding the reach of an Ethernet network is of little use if data integrity is not preserved. Therefore, in addition to choosing the appropriate PoE type for their application, designers must also select magnetics and filters that maintain signal integrity by screening out various kinds of electronic noise.

ICMs combine connectivity and filters

Integrated connector modules (ICMs), like those in the MagJack series (Figure 1) from Bel, house magnetics within the same printed circuit board (PCB) footprint as the RJ45 Ethernet jack to maximize layout efficiency.

Figure 1: MagJack ICMs support deployment of PoE by combining RJ45 connectors with robust filtering magnetics and EMI/RFI shielding in compact packages. (Image Source: Bel)

ICMs in the MagJack line support a variety of Ethernet speeds ranging from 10BASE-T (10 Mbps) through 10GBASE-T (10 Gbps) while transmitting up to 120 W of power. Configurations from single-port to two stacked rows of eight ports to a combination of RJ45 and USB-A 2.0 ports provide flexibility for a variety of applications.

Designers also have the flexibility of choosing how MagJacks mount to a PCB. Through-hole, surface-mount technology (SMT), pin-and-paste, and press-fit configurations are all available in the MagJack line. Designers may consider thermal management, serviceability, board thickness and insertion stress, and manufacturability when choosing the best mounting technology for their application.

For instance, SMT, pin-and-paste, and through-hole PCB mounting technology are good choices for mass production when a solder production line is already in place. The soldered pins in through-hole MagJack ICMs create a robust mechanical connection, which—along with the simple, cost-effective attachment design—has long made through-hole solder termination the traditional choice to ensure reliability in rugged industrial or outdoor environments.

On the other hand, a press-fit design, such as the compliant phosphor-bronze pin design on press-fit MagJack units, is a better choice in applications where designers want to avoid exposing the PCB or components on it to excessive heat during manufacturing. The jacks’ 98 pins press into holes in the PCB that are coated in conductive metal. The multiple pin connections also create a stable connection for the insertion and repeated removal of the RJ45 connectors without the risk of solder-joint fatigue. This design is also easier to service in the field because no solder rework is required.

Without the need for solder tails, press-fit ICMs can attach to PCBs 2.05 mm thick or thicker, including stacked backplanes. This gives designers greater flexibility to use PCB space efficiently, even in applications like cameras with edge processing capability that require a high density of networking ports and high-power PoE.

Conclusion

Whether they use compliant press-fit pins or pins that are soldered into through holes, ICMs like those in the MagJack series make industrial Ethernet networks possible. Their integrated magnetics preserve signal integrity in a compact package, even in PoE applications carrying up to 120 W of power along with Ethernet data.

The combination of robust and compact design, signal filtering, and power transmission makes MagJack ICMs integral to industrial Ethernet networks, allowing designers to advance AI and ML applications without adding cabling or manufacturing steps.