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Power Supplies 7-9
7
The PCM incorporates an AC inrush limit circuit and two precharge inputs
(3.3V and 5V) that enable it to be hot-pluggable into a live centerplane. A
current sharing scheme on the 2.0V, 3.3V, and 5V outputs enable the PCM to
operate in a parallel redundant mode. A maximum of eight PCMs are used
together in the redundant current sharing.
The 5V output is parallel in a system with all other PCMs and the 5V output of
a peripheral power supply. The 2.0V and 3.3V outputs are parallel in a system
with all other PCMs.
7.4.1 Power Requirements
In general, if a PCM fails, the system boards will continue to be powered and
cooled by the other power supplies provided redundancy (an additional power
supply) is present. For example, if an Enterprise system needs a minimum of
three power supplies and four are present, then the system has redundancy.
However, fully configured Enterprise systems represent a different situation
and are always hot-pluggable. That is, an Enterprise 5000 or 4000 system with
seven or eight boards and four PCMs is hot-pluggable. (The peripheral power
supply acts as the “extra” power supply.) Similarly, an Enterprise 6000 system
with fifteen or sixteen boards and eight power supplies is also hot-pluggable.
(Only seven PCMs are required to power sixteen active boards; the eighth PCM
is “extra.” However, the eighth PCM is required for cooling purposes.) See
Table 7-3.
Note – The presence of an additional (extra) PCM in the system provides
redundancy and allows hot-plug of PCMs.