Compact SPE Interfaces for Space-Constrained Ethernet Designs

Single Pair Ethernet (SPE) brings standardized Ethernet connectivity to applications where routing conventional Ethernet cabling can be impractical or too expensive. But SPE supports multiple standardized mating interfaces, so designers must match the connector choice to the mechanical, environmental, and density requirements of the application.

In industrial automation, SPE can connect sensors, actuators, controllers, and other devices at the edge of the network. For building automation applications, it can link lighting, HVAC, security, and environmental sensors. It is also suitable for transportation and automotive applications, where its reduced cabling footprint can help address space and weight constraints.

SPE extends Ethernet over a single twisted pair, giving sensors, controllers, and other edge devices an IP-based physical-layer connection to switches, gateways, and broader Ethernet infrastructure. Connected nodes can communicate over IP-based networks and, where the architecture supports it, exchange data with plant systems and cloud-based monitoring or analytics platforms.

By replacing some point-to-point links, field-level networks, or dedicated fieldbus connections, SPE can reduce separate wiring and communications infrastructure while helping manufacturers integrate smaller, more distributed devices into connected production environments. Using one twisted pair can simplify cabling, cut wiring weight and bulk, and avoid crosstalk issues that come with multi-pair Ethernet cables.  

Network-level benefits only translate into a workable product design when the SPE mating interface aligns with the equipment environment, available board or panel space, and the required data and power performance.

Interface choices

The mating interface is an important design consideration in these extended industrial Ethernet networks. IEC 63171 defines multiple standardized SPE mating interfaces to address different mechanical, environmental, and application requirements, giving designers a choice of standardized interface options.

For protected equipment, control panels, and enclosure-mounted connections, the compact IEC 63171-1 (Type 1) interface supports smaller, higher-density SPE connections. In harsher mechanical or environmental settings, designers may need to consider other IEC 63171-x interfaces, including ruggedized M8 or M12 configurations.

An SPE connector solution should ensure the mating interface, cable connection, electrical performance, power delivery, and product features will work together as intended in the finished application. For equipment where the connector is protected within the product or an enclosure, the compact Type 1 interface can provide a smaller, high-density connection for SPE data and power requirements.

The IEC 63171-1 interface employs a form factor and mating geometry derived from LC simplex fiber connectors but replaces the optical interface with electrical contacts for transmitting SPE over copper. Compared to traditional RJ45 Ethernet interfaces, the two-pole SPE connector can reduce the footprint of PCB installations by 50% or more. 

Taking advantage of defined mating specifications

Stewart Connector SPE Connector System products from Cinch Connectivity Solutions use the space-efficient, two-contact IEC 63171-1 interface for PCB-based equipment connections. Because the products are built around a defined mating specification, designers can use an established connector geometry instead of creating a custom interface and having to define interoperability requirements.

The Stewart Connector SPE portfolio includes PCB jacks and mating cable assemblies designed as complementary components. The shielded, right-angle, through-hole jacks support 1000BASE-T1, 100BASE-T1, 10BASE-T1L, and 10BASE-T1S, as well as Power over Data Line (PoDL) Classes 1–15 and SPE Power-over-Ethernet (SPoE) applications.

A compact SPE connector may not leave room for an LED immediately adjacent to the connector opening. Cinch's Stewart Connector SS-69000-001 SPE Ethernet jack with light pipe (Figure 1) incorporates a molded, transparent optical element that captures light from a PCB-mounted LED and guides it to the front of the connector, making port status visible at the interface.

Figure 1: The Stewart Connector SS-69000-001 SPE jack integrates a light pipe optical element for port status visibility. (Image source: Cinch Connectivity Solutions)

For designs where status indication is handled elsewhere on the product, or where the goal is to minimize features at the connector opening, Cinch also offers a light-pipe-free SS-69000-002 jack. The two jack versions share the same SPE interface and core electrical capabilities, so each can take advantage of Stewart Connector IEC 63171-1 cable assemblies in 1, 2, and 3 m lengths (Figure 2).

Figure 2: Preassembled Stewart Connector SPE cables in 1, 2, and 3 m lengths utilize male IEC 63171-1 plugs at both ends, providing a defined mating solution for the SS-69000-001 and SS-69000-002 PCB jacks. (Image source: Cinch Connectivity Solutions)

Conclusion

Selecting the right SPE connector ultimately hinges on matching the mating interface to the equipment environment, available space, and required data and power performance. For protected, space-constrained designs, Stewart Connector IEC 63171-1 SPE jacks and compatible cable assemblies give designers a defined, two-contact interface that can bring Ethernet connectivity to edge devices while supporting PCB density, PoDL, and SPoE power delivery.