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Intel NetStructure
®
MPCMM0002 Chassis Management Module
July 2007 Hardware TPS
Order Number: 309247-004US 21
Module Components—MPCMM0002 CMM
4.10 ADM1026 Controller
An Analog Devices* ADM1026 controller monitors the on-board voltages and manages
the thermal sensors. The processor communicates with the ADM1026 through an I
2
C
bus.
4.11 Hot Swap Controller
The CMM uses an LTC4250AH* Hot Swap controller to ramp voltages and watch for
over-current conditions. If the CMM draws more than 2.5 A for more than 500 µs, the
Hot Swap controller terminates.
The Hot Swap controller waits for the enable signals (short pins tied to each return) to
connect before ramping up the circuitry on the CMM. Similarly, if a CMM is pulled out of
the system, the Hot Swap controller immediately cuts power to the board.
4.12 Ride-Through Support
Many carriers require equipment to survive a 5 ms period without any power in order to
survive power glitches due to short circuit, power switchovers, etc. Section 4.1.4.3 of
the PICMG 3.0 specification requires boards to survive this 5 ms drop-out and
recommends that other chassis elements also have capability to ride through these
transients.
The MPCMM0002 CMM module meets this requirement. The CMM will survive the zero
volt transient described in Table 4-4 of the PICMG 3.0 specification. Large bulk
capacitors next to the DC-DC power converters provide this hold-up capacity.
4.13 IPMB Isolation Logic
In a carrier-grade system it is important to prevent cascaded failures; that is, a failure
in one element that affects other system elements and causes them to fail or lose
significant functionality. A shared bus is more sensitive to a single item impacting other
elements than a simple point-to-point system. This is one reason the MPCMM0002 CMM
chassis management module implements the hybrid dual IPMB star topology outlined in
Section 6.1, “IPMB Routing” on page 28.
Some IPMB channels are dedicated links between the CMMs and an individual blade;
this type of link is called a star. Some IPMB channels are shared among several devices,
and this type of link is called a bus. The star and bus elements have different isolation
logic in the CMM.
4.13.1 Dual Star IPMB Isolation
The dual star IPMBs on the MPCMM0002 CMM use MOSFET-controlled isolators to
disconnect all the radial IPMB signals automatically if power fails on a CMM. The
isolation circuit is pictured in Figure 5. The hardware ensures that the CMM is isolated
from the dual star IPMBs if power fails.