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Also supported is VITA 48
REDI (Ruggedized Enhanced
Design Implementation). Part
of VITA 48 has a defined pitch
–the interval on a backplane
of each module–of 1.0”. This is
an increase over the 0.8” pitch
of the older VME standard, a
change which permits higher
power levels and taller components.
In addition, air, liquid,
and conduction cooling parameters
are defined within VITA 48
to provide uniform packaging
alignment.
Although all semiconductor
devices are subject to damage by
ionizing radiation, high density
semiconductors are the easiest
to be damaged by ionizing radia- Figure 2: Typical VITA 62 3U
tion. A NED (Nuclear Event
Detect) input is supported by
electrical configuration
VITA 62 to shut down power during such an event.
SENSE pins permit feedback of +12V, +5V and +3.3V to the power
supply. These voltages compensate for IR (current-resistance) drop
at the connection and provide correction to some
of the transients produced by load surges. SHARE
pins facilitate current balancing between power
supplies operated in parallel. The VBAT pin permits
an on board battery to supply power to system nonvolatile
memory. This is important to save system
CMOS settings and other low power volatile storage.
The block diagram in Figure 2 shows VITA 62 3U
power supply electrical connections. VS1, VS2 and
VS3 show DC outputs +12V, +3.3V and +5V respectively.
Current sharing signals represented by the
SHARE signals are sent between power supplies in a
sharing configuration. SENSE lines feedback signals
to regulate power output voltages VS1, VS2 and VS3
to the remote load. VITA 46.11 Bus is the I2C link to
the Chassis Manager. The NED input indicates the
presence of Nuclear Event. ACL and ACN are AC line
(hot) and neutral.
Intelligent Platform Management Bus
support
VITA 46.11 IPMB (Intelligent Platform Management
Bus) is focused on ensuring reliable systems
operation and is referenced in VITA 62. VITA 46.11 specifies that
an I2C serial bus be used for communication between modules and
the Intelligent Chassis Manager. This link facilitates sophisticated
systems management through onboard processor control and
monitoring. Monitoring on board sensors permits an Error Log to
be created that flags conditions that may have contributed to failure.
SPECIAL FEATURE
Conditions in the field can never fully be anticipated by any test since
an unusual set of circumstances may act together to cause system
failure. The Error Log produced by the Intelligent Chassis Manager
is thus extremely important because it documents conditions in the
field that led to failure. It is important that the cause of failure be
identified for future maintenance and design. The design engineer
must be fully aware of events leading to failure. This is where the
Error Log is important, it keeps a log of critical parameters such as
vibration, humidity, and temperature.
For example, the Error Log may indicate that a particular board
has a problem with temperature caused by cooling fans. The System
Manager can then be programmed to lower the fan speed so that the
temperature of the board is just below its upper specification.
Critical Vita 62 Power Supply Characteristics
VITA 62 power supplies have unique challenges in modern deployment
systems. Smart VITA 62 power supplies have voltage rail
control which enables them to be individually sequenced, up and
down. This provides critical sequencing to CPU cards, FPGA cards
and other VITA 65 cards, which are sensitive to which voltage comes
up first.
Power sharing between two or more supplies can be advantageous
if total current requirements exceed that which can be delivered by
a single supply. It can also be advantageous if there is at least one
supply more than that required. Referred to as N+1 redundancy, if
Figure 3: Examples of 3U VITA 62-compliant power supplies from Dawn VME Products.
The PSC-6236 air-cooled design on the left includes a front panel with connections, while
the equivalent conduction-cooled LRU on the right clearly shows wedgelocks for cold
plate cooling. These compact PSUs can source 400 W over a wide temperature range.
one power supply fails the system can still supply the required current
using the remaining functional supplies. It also means that
power supplies can be hot swapped. In addition, N+1 redundancy
reduces the power dissipated by each supply and reduced power
means a lower onboard temperature.
www.eecatalog.com/vme 19