Power Down; Cooling System Functional Description - Cisco ASR 9001-S Overview And Reference Manual

Chapter 2 Functional Description
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Power Down

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Cooling System Functional Description

The Cisco ASR 9000 Series Routers chassis is cooled by removable fan trays. The fan trays provide full
redundancy and maintain required cooling if a single fan failure should occur.
In the Cisco ASR 9010 Router, the two fan trays are located one above the other below the card cage and
are equipped with handles for easy removal.
In the Cisco ASR 9006 Router, the two fan trays are located above the card cage, left of center, and side
by side. They are covered by a fan tray door hinged at the bottom, which must be opened before removing
the fan trays.
In the Cisco ASR 9904 Router, a single fan tray is located to the left of the card cage accessible from
the rear, and is equipped with handles for easy removal.
In the Cisco ASR 9922 Router, the two top fan trays are located between the top and middle cages, while
the two bottom fan trays are located between the middle and bottom cages. The two bottom fan trays are
inserted upside down compared to the two top fan trays. In the Cisco ASR 9912 Router, the two fan trays
are located above the line card cage. Each fan tray holds 12 axial fans and includes a controller that
reduces the speed of the fans when the chassis temperature is within limits, thereby reducing the
generation of acoustic noise. The fan controller also senses and reports individual fan failures.
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The soft-start circuit in the logic cards takes 100 milliseconds to charge the input capacitor of the
on-board DC/DC converters.
The card power controller, MCU, enables the power sequencing of the DC/DC converters and POLs
through direct communication using a PMBus interface to digital controllers such as LT7510 or
through a digital wrapper such as LT2978.
The output of the DC/DC converters ramp up to regulation within 50 milliseconds maximum. after
the program parameters are downloaded to each POL and On/Off control pin has been asserted.
Power conversion is disabled by toggling the Power On/Off logic switch in the power tray to OFF
position.
The DC/DC modules in the power tray stays within regulation for a minimum of 3.5 milliseconds
after the Power On/Off logic switch is disabled.
The –54V DC to the logic card ramps down to –36 VDC in 3.5 milliseconds minimum from the time
the DC/DC modules starts ramping down from its minimum regulation level.
The DC/DC converters powers off immediately after the On/Off pin is deasserted.
The output of the DC/DC converters stays in regulation for an additional 0.1 millisecond.
Cisco ASR 9000 Series Aggregation Services Router Overview and Reference Guide
Cooling System Functional Description
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