Communications Insider: March 2009: Volume 4 Issue 1

Rugged MicroTCA.1 Nears Adoption

As you may remember, efforts by PICMG® members to develop a rugged version of MicroTCA™ eventually resulted in the formation of three distinct Sub-Committees: Rugged MicroTCA.1 (Air-Cooled), Hardened MicroTCA.2 (Air-Cooled), and Hardened MicroTCA.3 (Conduction-Cooled).

At this time, only the Rugged MicroTCA.1 Air Cooled specification (µTCA-R) has progressed to the point of being submitted to PICMG for adoption and release. The Hardened versions are targeted toward more demanding applications which require greater resistance to both thermal and mechanical stresses. As a result, the Hardened specifications have required more time to develop.

With the current proposal of four specifications for MicroTCA in PICMG, it was believed that an overview document, non-normative (no requirements), was needed to introduce each spec and the concepts & reasons for each, plus interrelationships. This document would be called the MicroTCA Guide, and it would provide an overview of MTCA.0 through MTCA.3. The diagram below (from the Rugged MTCA.1 Sub-Committee work) helps to clarify the relationships of the various specifications.

Sub-Committee Work Complete The PICMG technical/IPR review for the MicroTCA.1 Air-Cooled Specification D0.91 began in early December of 2008. There were several Change Requests from this review, and no IPR issues were identified. The Sub-Committee suspended activity during the 30-day technical review cycle, but began meeting again on January 13, 2009 to review the Change Requests, propose and make changes as needed (or reject the Change Requests and report that back to PICMG). Sub-Committee work proceeded through January of 2009, with closure on Change Requests and generation of a Release Candidate Specification for release to PICMG and adoption. This specification, Rugged MTCA.1 Air-Cooled R1.0 RC1, is the result of the effort. The Rugged MicroTCA.1 Sub Committee has now ended its formal activities, and the specification has been delivered to PICMG for adoption and release.

Source: PICMG

Suitable for Many Applications
From the very beginning, application requirements have been the defining force behind efforts to develop rugged versions of MicroTCA. The targets for Rugged MicroTCA.1 included applications such as transportation, outside-of-plant telecom, civil aviation and industrial automation. Harsh military, hazardous industrial and other extreme application environments were assigned to Hardened MicroTCA.

The good news is that, as it currently stands, Rugged MicroTCA.1 is indeed a suitable option for the applications it has targeted, based on the known demands of the relevant industries. Rugged MicroTCA.1 should be a welcome addition to the current range of options available to system designers.

Worth the Wait
The process of getting this specification ready for a vote has been long and somewhat difficult, but the end result is quite impressive. Consider, for example, that this new rugged standard will make it possible in certain settings for a telecom service provider to deploy the same standardized AdvancedMC modules in a central office or a outdoor cabinet. And many applications that require a "tougher" system will now be able to take advantage of MicroTCA's capabilities.

As currently written, air-cooled Rugged MicroTCA.1 would allow board manufacturers to claim compliance with thermal specification independently of mechanical specification. Each of these levels is backed up by an explicit testing protocol, including setups and procedures. Since there are two levels of thermal and mechanical severity, there will be 9 conceivable MicroTCA variants as shown in the table.

Hardened MicroTCA.3 Work Continues
As I mentioned earlier, the Hardened MicroTCA standards have a steeper hill to climb. They are targeting applications where the stresses on electronics gear are extreme. However, that is not to say there's been no progress.

The Hardened MTCA.3 Conduction-Cooled Sub-Committee is very active, with weekly meetings covering mechanical, connector and environmental issues associated with implementing MicroTCA and AdvancedMC™ in the Conduction-Cooled world of Mil/Aero/industrial. There continues to be a great deal of participation. There has not been as much activity on the Hardened MicroTCA.2 Air-Cooled Specification and the future of the effort is unclear. However, a conduction-cooled variant of MicroTCA would appear to be a near certainty in the future.