Technology In Context
Rugged Applications
Mechanical Aspects of VPX and VPX-REDI Enhance Functionality and Ruggedness The VPX standard brings not only enhanced and denser modern I/O, but also improvements for cooling that enable more functionality and robust ruggedization. by I van Straznicky Curtiss-Wright Controls Embedded Computing
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ecent design wins involving VPX (VITA 46/48) single board computers and VPX Gigabit Ethernet Switch engines, particularly for the military’s high-profile Future Combat Systems (FCS) program, illustrate the rapid rate of adoption and success that the new VPX standard has experienced in the short couple of years since the first products were made available. VPX, in some ways the “next-generation” VME board architecture, was, like VME, defined and standardized by the VITA Standards Organization (VSO). It leverages much of the goodness of the venerable VME standard, such as the 6U form factor and support for the VME electrical specification for backward compatibility, while adding significantly greater bandwidth, ruggedization and ESD protection, among other enhancements. VPX is well on its way to establishing itself as VME for the 21st Century for high-end aerospace and defense applications. To appreciate the attributes of VPX and VPX-REDI, the complementary standard defined by VITA-48, it is important to understand the mechanical aspects at the plug-in module level, in addition to the electrical characteristics. One of the reasons that VPX is becoming popular so quickly is that it is both revolutionary and
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October 2008
Liquid In
Liquid Out
Figure 1
Among the VPX standards, support for advanced cooling methodologies is support for Liquid Flow-Through (LFT) cooling, in which liquid is brought in from the chassis through quick disconnect (QD) connectors, routed across the module to provide highly efficient cooling, and exits the module through another QD connector.
evolutionary. It is revolutionary in that it provides a vast amount of high-speed differential I/O for new serial fabrics such as Serial RapidIO, PCI Express and 1/10Gbit Ethernet, as well as high-speed I/O interfaces for video, storage and sensor capa-
bilities. And it is evolutionary because it maintains support for the VME databus providing compatibility with legacy boards. From a mechanical perspective, VPX and VPX-REDI also maintain support for the standard 6U and 3U form factors long preferred by the military for rugged applications and support for both PMC and the newer XMC mezzanine cards. 6U VPX modules offer an optimal balance between functional density and ruggedness, while 3U VPX offers the advantage of compactness for space-constrained applications. The 3U VPX form factor also delivers a significant amount of I/O for a small card, essentially dedicating the entire P2 connector location to I/O. One of the key mechanical attributes of VPX and VPX-REDI is the introduction of a high-speed connector. This new connector, the 7-row version of the Tyco MultiGig RT2, has been modified specifically for VPX, with changes such as a shortened length to fit onto typical conduction cards, and a thicker gold contact plating for better harsh environment resistance. The new connector set also includes hardware that provides safety grounding in addition to alignment and keying (Figure 1). The same connectors and alignment hardware are used in both 6U VPX and 3U VPX form factors along with PMC and XMC support.