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Chapter 2 Environmental Monitoring 31
Switching Power On and Off
The on-board voltage controller allows power to the CPU of the Netra CP2500 only
when the following conditions are met:
■ The VDD core-1.1-volt supply voltage is greater than 1.0 volts (within 10% of
nominal).
■ The 12-volt supply voltage is greater than 10.8 volts (within 10% of nominal).
■ The 5-volt supply voltage is greater than 4.5 volts (within 10% of nominal)
■ The 3.3-volt supply voltage is greater than 3.0 volts (within 10% of nominal).
The controller requires these conditions to be true for at least 100 milliseconds to
help ensure the supply voltages are stable. If any of these conditions become untrue,
the voltage monitoring circuit shuts down the CPU power of the board.
Inlet, Exhaust, and CPU Temperature Monitoring
The CPU diode sensor reading may vary from slot to slot and from board to board in
a system, and is dependent primarily on system cooling. As an example, a system
might have sensor readings for the CPU diode from 35˚C to 49˚C with an ambient
inlet of 21˚C across many boards, with a variety of configurations and positions
within a chassis. Care must be taken when setting the alarm and shutdown
temperatures based on the CPU diode sensor value. This sensor typically is linear
across the operating range of the board.
The exhaust sensor measures the local air temperature at the trailing edge of the
board for systems with bottom to top airflow. This value depends on the character
and volume of the airflow across the board. Typical values in a chassis may range
from a delta over inlet ambient of 0˚C to 12˚C, depending on the power dissipation
of the board configuration and the position in the chassis. The exhaust sensor is
nonlinear with respect to ambient inlet temperature.
The inlet sensor measures the local air temperature at the leading edge of the board
on the solder side under the solder-side cover. This value typically can range from a
reading of 0˚C to 13˚C above inlet system ambient in a chassis. Care must be taken to
understand the application and installation of the board to use this temperature
sensor.
A sudden drop of all temperature sensors close to or near room ambient temperature
can mean loss of power to one or more Netra CP2500s.
A gradual increase in the delta temperature from inlet to outlet can be due to dust
clogging system filters. This feature can be used to set service levels for filter
cleaning or changing.