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Cisco ASR 9000 Series Aggregation Services Router Overview and Reference Guide
OL-17501-09
Chapter 2 Functional Description
Power System Functional Description
AC System Operation
This section describes the normal sequence of events for system AC power up and power down.
Power Up
1. AC power is applied to the power tray by toggling the user’s AC circuit breakers to the ON position.
2. AC/DC power supplies are enabled by toggling the Power On/Off logic switch located in each of the
power trays to the ON position.
3. AC/DC modules in the power trays provide –54 VDC output within six seconds after the AC is
applied.
4. The soft-start circuit in the logic cards takes 100 milliseconds to charge the input capacitor of the
on-board DC/DC converters.
5. The card power controller MCU enables the power sequencing of the DC/DC converters and points
of load (POLs) through direct communication using the PMBus interface to digital controllers.
6. The output of the DC/DC converters ramps up to regulation within 50 milliseconds maximum after
the program parameters are downloaded to each POL and the On/Off control pin has been asserted.
Power Down
1. Power conversion is disabled by toggling the Power On/Off logic switch to the OFF position or
unplugging the power cords from the AC power source.
2. The AC/DC modules in the power trays stay within regulation for a minimum of 15 milliseconds
after the AC power is removed.
3. The –54 V to the logic card ramps down to –36 V in 15 milliseconds minimum from the time the
AC/DC modules starts ramping down from its minimum regulation level.
4. The DC/DC converters turn off immediately after the On/Off control pin is deasserted.
5. The output of the DC/DC converters stays in regulation for an additional 0.1 millisecond.
DC Power Trays
The DC power tray (see Figure 2-60) provides two power feed connector banks: A feed and B feed.
System communication is through a I2C cable from the backplane.
DC Tray Power Switch
Each DC power tray provides a single-pole, single-throw power switch to power on and off all of the
power modules installed in the tray simultaneously. When the power modules are turned off, only the
DC output power is turned off; the power module fans and LEDs still function. The power switch is on the
front panel.
DC Power Tray Read Panel
Figure 2-60 shows the rear panel of the power tray for the version 1 power system. Figure 2-61 shows
the rear panel of the power tray for the version 2 power system.
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