VITA 76 provides for high-bandwidth I/O in a rugged MIL-38999 circular connector

The /aero markets have been moving rapidly toward implementing into their systems many of the commercial standards such as PCI Express, Ethernet, USB, SATA, DisplayPort, and so on. In recent years, the challenge has become the transfer of large amounts of high-bandwidth data between ever-smaller enclosures via a medium. However, the good news is that ( Cable Standard) provides for a rugged high-bandwidth I/O interconnect packaged in a rugged MIL-38999 circular format.

Accordingly, the 76 working group has proposed using ’s Hercules Interconnect System – specifically its contact interface, consisting of a high-density grid of Hermaphroditic (Hermi) contacts that are inherently rugged by the nature of the interface’s two-contact point design. The “Hermi” contact is an ideal interconnect for the high-density rugged requirements of VITA 76 in MIL-38999 shell size No. 9 with two differential pairs through shell size No. 23 with 44 differential pairs. The adjacent contacts are on .050" pitch and .105" row to row and staggered to minimize crosstalk. The contact arrangement carefully controls the impedance and minimizes the resonances present through the cable termination, plastic header, and hermaphroditic mating. The contact design gives very low insertion and return losses as well as very low crosstalk between the data pairs, exceeding 10 Gbps data rates per differential pair regardless of transmission protocol. Hercules will accommodate multiple protocols such as InfiniBand, USB 2.0 and 3.0, PCIe Gen2, Serial , Ethernet, 10 G Ethernet, CX4, SAS, and SATA.

Copper and active optic components

A significant benefit of the VITA 76 interconnect system is the accommodation of both copper and Active Optic (AO) in one interface. The panel mount MIL-D-38999 will be identical regardless of being a copper or AO I/O. The mating cable plug will allow for the egress of copper bundled cable or for the attachment of an AO module allowing for the egress of fiber cable.

Compatibility with other VITA standards

The VITA 75 Rugged Small Form Factor working group has been working closely with the VITA 76 working group for the very reason that VITA 76 exists. There is no alternative high-density, high-bandwidth I/O available for transferring large amounts of data between enclosures that are being utilized in mil/aero applications today. The VITA 76 interconnect system allows for multiple protocol I/O through a single MIL-38999 interface on a VITA 75 Small Form Factor .

Much yet to be done

While the commercial development of the interconnect system is moving along and environmental testing will be completed during Q1 2012, there remains much work within the VITA 76 committee to bring the new standard to fruition. The AO portion of VITA 76 will require more time for development, and the committee’s work on the copper version should be complete by mid 2012.

Kenneth Braund is a Business Manager responsible for the Hercules product line at Meritec. He has more than 40 years of experience in the design, manufacture, and marketing of interconnect systems. He can be contacted at

Alan Roath is a Senior Project Engineer responsible for the Hercules product line at Meritec. He has more than 25 years of experience in the design and manufacture of interconnect systems. He can be contacted at