Datasheet

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AB and AB-friendly connectors
daughtercard backplane rear I/O board
Fig. 3: CompactPCI 6U configuration
Improved guiding with AB-modules:
In accordance with the equipment practice each
front side arrangement of
har-bus
®
HM connectors
shall have at least one A-module per slot to ensure
that the connector can accommodate ± 2 mm
alignment tolerances in rack systems.
On some rear I/O arrangements the A-module's
alignment capability cannot be utilised, because
only B-modules are used for feed through.
Consequently AB-modules were introduced to
ensure guiding capabilities where formerly only
B-modules were used. Those AB-modules represent
a combination of A- and B-modules and are
specified in CompactPCI by PICMG 2.0 Rev. 3.0
for certain rear I/O applications.
The AB-modules have guiding pegs similar (but not
mating compatible to prevent mismating) to those of
the A-module providing the same proven mating
tolerances of ± 2 mm. The AB-modules have no
coding center but are fully equiped with contacts
in order to maintain the full density as per the
B-modules.
The AB-female connector mates either with an
AB-shroud or with AB-male connectors. The
centered pin positions of the shielding rows of male
connectors are simply equipped with short spill
contacts (if standard connector and shroud are
used). This prevents that the guiding peg of the
female AB-module stubbing on the feed through
contacts of the front side's fixed connector. These
fixed connector loadings are called AB-friendly.
The AB-male connector will not be equiped with
shielded contacts in the centre where the guiding
peg will engage.