FireWire: Connected Solution for Automotive Applications using Shielded Twisted Pair Cable and Connector Construction

Contributed by:
Mike Gardner, Marketing Manager for Automotive
Molex Inc., Lisle, Illinois, USA

Most of us thinking of FireWire connected solutions would quickly envision cables and connectors linking consumer devices and maybe industrial type applications.  But embedded automotive devices?  Never gave it a thought!  But all that has changed with the release of the 1394 Trade Association's Copper Automotive standard this past summer.

Having a copper interconnect solution for automotive embedded systems opens the door for wide range of new and exciting possibilities within the vehicle.  A great deal of focus is being placed on the need for the next generation in-vehicle network solution to enable multimedia content along with other vehicle functions to be shared throughout the vehicle. The 1394Cu specification is an extension of the IDB-Automotive POF specification previously released and allows various automotive grade high speed copper interconnect media solutions, making it possible to deliver a robust IEEE 1394 link between embedded electronic control units (ECUs).  While there are multiple copper media solutions offered in the specification, "Shielded Twisted Pair" (STP) cable technology provides the same low cost cabled technology widely deployed by 1394 (FireWire) consumer cabled links.  The 1394Cu specification offers the opportunity to eliminate the need for power within the link while also specifying the copper link budget to deliver a minimum distance of 8 meters within the vehicle at S800 speeds.  This includes up to 5 in-line connections to facilitate the vehicle install environment.

Shielded Twisted pair automotive grade solutions still deliver the flexibility and benefits of tightly coupled differential pair construction, providing noise immunity and needed impedance controlled cable.  Signal pair drain wires separate to that of the overall cable shield drain, which helps to control the common mode return current that greatly contributes to the emissions that automakers are always working hard to eliminate.  This separation of signal pair drains wire to that of overall cable shield in STP cable construction further allows integrators to manage EMI susceptibility and radiation through two distinct paths.

The use of STP cable construction also allows additional signal or power lines to be intergrated into the cable construction, offering potential for expanded application in dedicated links.  

This flexibility to add or remove functionality within the STP cable construction allows cost to be tailored to the need and functionality of the application specifics of the vehicle.  This flexibility is why STP cable construction continues to be the most widely deployed copper link solution for all industries and ideally suited to be the chosen approach for in-vehicle integration as these high speed embedded solutions address the growing needs of network demands the auto industry seeks to deploy in future vehicle platforms.

Selecting the right copper interface at these initial stages of in-vehicle integration can save a significant amount of time, resource and money. The combination of Shielded Twisted Pair technology and IEEE 1394 can provide a robust and cost affective platform for automakers to build upon with high data rates, guaranteed bandwidth and low latency, excellent reliability, power and data options over a single cable, and a common industry standard offering scalability for the future.

Molex recently released its HSAutoLink™ family of automotive grade high speed cabled interconnect products making it possible to deliver a robust IEEE 1394 link between embedded electronic control units (ECUs). HSAutoLink™ accomplishes this with the same low cost "Shielded Twisted Pair" (STP) cable technology widely deployed by 1394 consumer cabled links.