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Bench Talk for Design Engineers

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Bench Talk for Design Engineers | The Official Blog of Mouser Electronics


Test Kits Speed SPE Automotive Designs Rick Nelson

(Source: metamorworks/Shutterstock.com)

Single-pair Ethernet (SPE) shows promise in the automotive industry, serving applications ranging from infotainment to advanced driver assistance. The proliferation of sensors and related features is driving the move toward SPE. As the One-Pair Ether-Net (OPEN) Alliance Special Interest Group (SIG) points out, adding a feature traditionally required the addition of a new electronic control unit (ECU). But with today’s vehicles having an average of 50 ECUs and with some having more than 200, this approach becomes impractical. Consequently, the industry is moving to zonal service-oriented architecture. New services can be added to a high-performance ECU that communicates via SPE to multiple sensors and actuators. Effective deployment of SPE in vehicles requires advanced connector technology and a fast, accurate way to evaluate the connectors. Two new signal-validation kits—the enetSEAL+ Signal Validation Kit and HDSCnet+ Signal Integrity Test Kit—can help with this latter task.

Connector Portfolio

TE Connectivity’s offerings for SPE include the enetSEAL+ and HDSCnet+ connector portfolios. The enetSEAL+ connector supports wire-to-wire and wire-to-board connections in harsh conditions for multifunction displays, telematics, telemetry units, infotainment modules, advanced driver assistance systems, and media access controllers. It can connect external cameras and sensing modules using SPE differential signal-transmission communication protocols.

The HDSCnet+ rugged, heavy-duty thermoplastic connector combines the TE Connectivity HDSCS connector interface with the company’s single-pair Ethernet MATEnet modular, scalable, miniaturized automotive Ethernet interconnection system. HDSCnet+ supports wire-to-wire and wire-to-device connections and will soon support wire-to-board connections. It enables multiple hybrid interfaces, combining SPE in addition to power and scalability for unshielded or shielded twisted-pair cable. MATEnet supports up to 1Gb/s, according to IEEE 100BASE-T1 and 1000BASE-T1 standards, and up to 4Gb/s based on alternative technologies. TE’s NanoMQS terminals are compatible with both unshielded twisted pair (UTP) and shielded twisted pair (STP) variants. Application examples include in-vehicle networking (1000BASE-T1) and rearview cameras (100BASE-T1).

Test Kits

To support design involving these connector technologies, TE Connectivity offers two test kits. The enetSEAL+ Signal Validation Kit supports 100BASE-T1 (IEEE 802.3bw) 100Mb/s connections, enabling designers to validate the enetSEAL+ connector system to the TC2 OPEN Alliance specifications for SPE communication over UTP cable.

The kit contains two test-board assemblies populated with one enetSEAL+ 180° header and two SMA connectors. It also contains five 3m jacketed UTP 20AWG cable assemblies that can be mated to create a 15m total cable link between the two test boards (Figure 1). This link replicates the 100BASE-T1 specification that allows for the maximum of four inline connections within a channel, allowing the engineer to validate a full 15m whole communication channel (WCC) to meet 100BASE-T1 TC2 specifications.

Figure 1: The enetSEAL+ Signal Validation Kit includes two test-board assemblies and five 3m jacketed UTP cable assemblies. (Source: Mouser Electronics)

The HDSCnet+ Signal Integrity Test Kit for 100BaseT1 100Mb/s connections allows engineers to validate TE’s HDSCnet+/MATEnet connector system to the TC2 Open Alliance specifications for SPE communication over jacketed UTP cable. The kit contains two test boards, each populated with one MATEnet 90° header and two SMAs. Like the enetSEAL+ kit, the HDSCnet+ kit includes five cable assemblies that can be mated to create a 15m total cable link between the two test boards. Engineers can remove one or more of the cable links to evaluate a shorter channel length.

Test Setup Example

The enetSEAL+ kit can serve as an example of how engineers can employ both kits. The parameters to measure include characteristic impedance differential mode (CIDM), return loss (RL), insertion loss (IL), longitudinal conversion loss (LCL), and longitudinal conversion transmission loss (LCTL). In addition to the kit, the equipment required includes a vector network analyzer (VNA) and a time-domain reflectometer (TDR).

A typical test setup for WCC evaluation includes the test cables, inline connectors, and a 10mm ± 0.5mm isolation support (εr ≤ 1.4) over an enlarged ground reference plane (measuring at least 1m x 2m). The kit’s test-board assemblies attach to both ends of the test-cable link assemblies, taking the place of what would be ECU connectors in an actual automotive implementation. In turn, the test-board assemblies connect to a VNA—for measuring mixed-mode S parameters, including RL and IL—or a TDR—for measuring CIDM.

Figure 2 shows a photograph of a TE Connectivity lab setup with cables arranged in a meander, held in place by wooden picks, to avoid parasitic coupling. After performing the measurements using the VNA and TDR, the final step is to compare measured results with the limit lines of the TC2 communications-channel specifications.

Figure 2: This TE Connectivity lab setup shows cables arranged in a meander to avoid parasitic coupling. (Source: Mouser/TE “enetSEAL+ Measurements Instructions”)

The signal integrity kit measurements will confirm that the connector and cable choices meet the required protocol performance. They provide designers with hands-on experience using the respective connector families.

Conclusion

As the number of ECUs in vehicles grows, automakers are moving to zonal service-oriented architectures. A high-performance ECU communicates via SPE to multiple sensors and actuators. Two test kits—the enetSEAL+ Signal Validation Kit and HDSCnet+ Signal Integrity Test Kit—help designers evaluate connector technology as they adapt SPE for their automotive system designs.



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Rick NelsonRick Nelson is a technical journalist who has served as executive editor of Test & Measurement World, chief editor of EDN, and executive editor of EE-Evaluation Engineering. He has also contributed to publications including Vision Systems Design and Electronic Design, and he has participated in many live panel discussions and webcasts. Rick has also held systems-engineering and product-development positions at General Electric and Litton Industries. He received his B.S.E.E. degree from The Pennsylvania State University.


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