Author: Manfred Schmitz, Technical Director of MEN Mikro Elektronik
PICMG CPLUS.0 – CompactPCI® Plus – allows to connect the I/O for peripheral slots also using the backplane. The current CompactPCI® standard already includes this concept, but the number of free pins is very limited, especially with 3U solutions.
CompactPCI® Plus offers the option of using up to 96 pin pairs or 192 single pins even for 3U boards. These pins are all embedded into ground pins and are therefore shielded. For 6U boards more than 300 pin pairs or more than 600 single connections are available.
Today's CompactPCI® boards (PICMG 2.x) are based on metric 2-mm connectors. CompactPCI® Plus (PICMG CPLUS.0) uses AirMax-typeconnectors of FCI or Amphenol instead. Apart from the higher pin density these connectors also come with a better transmission behavior with high frequencies. Of course this also benefits the I/O signals. This allows to achieve data rates of 10 Gb/s and more for differential signals.
For this to become possible, however, the pins of the connectors do not protrude through the backplane anymore. With the 2-mm connectors, the pins of the connectors that were press-fit from the front protruded to the rear side, and a plastic shroud was put over them from the rear. With the AirMax connectors, this is solved by pressing in connectors from the front and back of the backplane in the rear I/O area. The only prerequisite to do this is a specific thickness of the backplane.
The CPLUS.0 standard now defines ground pins between the signal pins following a dedicated pattern. If you look at the backplane from the rear, this pattern is mirrored. It is now an advantage of the AirMax connectors that there are no special ground pins in the connector. No problems occur when connectors are press-fit from two sides. Contrary to the common CompactPCI® standard, CPLUS.0 uses receptacle connectors instead of plug connectors on the backplane, so that once and for all, twisted pins are a thing of the past.
Conductive cooling is an effective way for systems in harsh environments to meet both the thermal and the mechanical requirements, for instance for application onboard aircraft, trains, or agricultural machines. I/O is normally connected exclusively via rear I/O in conductive cooling systems. CompactPCI® Plus is perfectly equipped for this.