XMC goes rugged with VITA 61 mezzanine interconnect standard
As embedded computing applications continue to evolve, multi-gigabit data rates have become commonplace. This expectation extends to the rugged embedded computing marketplace, where unique packaging challenges driven by adverse mechanical and thermal environments must also be managed. One of the newest technologies put forth by the VITA Standards Organization (VSO) is targeted at mezzanine constructions and detailed in the VITA 61 “Alternative Connector for XMC” aka “XMC 2.0” draft standard. VITA 61 is nearing completion and will advance the XMC architecture state-of-the-art both mechanically and electrically.
During VSO bimonthly meetings, discussion of past, present, and future technology reviews occur, clarifying the fact that the XMC (VITA 42) ecosystem could benefit from a more rugged mezzanine connector. Ideally, the new connector would fit on the existing 114-position XMC footprint, yet enable higher data throughput.
VITA 61 connector: Putting it all together
The VITA 61 connector is mechanically robust. The separable interface has MIL-C-55302 connector heritage, includes four points of contact on opposing axes, and is rated to a minimum of 500 mating cycles. The connector is rated at -55 ˚C to +125 ˚C. The connector also features protected socket contacts – eliminating contact stubbing as a failure mode – and a compliant solder tail for superior board attach performance (successfully completed 2,000 thermal cycles).
The VITA 61 connector enables some very high-speed signals and is baselined at 5 GHz at the current VITA 42 pin assignments. Significant headroom up to 7-12 GHz is available with alternate pin assignments. With very low insertion loss and crosstalk, it is envisioned to be capable well beyond what second- and potentially third-generation protocols will need.
The VITA 61 connector is flexible and has been designed to support the existing XMC stack heights of 10 and 12 mm. A third height of 18 mm has been added as a result of committee input. The additional stack height provides the ecosystem with more packaging alternatives to mitigate growing thermal challenges.
Finally, the VITA 61 connector provides the XMC community a very elegant upgrade path. Although the VITA 61 and VITA 42 connectors are not intermateable (as indicated by different specification numbers), the VITA 61 connector employs the exact same board attach footprint as the original VITA 42 connector. As a result, no changes to the printed circuit board layouts are necessary.
[As of press time] the VITA 61 XMC 2.0 draft specification is nearing maturity. Currently, the draft specification is going through ANSI ballot. When the ballot is closed, comments and suggested edits will be incorporated as appropriate and the draft finalized. It is envisioned this will occur mid-2011 and that the VITA 61 XMC 2.0 specification will be completed and released before year’s end.