CP3005-SA – Rev. 0.6 Preliminary
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Thermal Considerations
The thermal characteristic graphs shown in the following sections are intended to serve as guidance for reconciling
the required computing power with the necessary system volumetric airflow over the ambient temperature. The
graphs contain two curves representing upper level working points based on different levels of average CPU
utilization. When operating below the corresponding curve, the CPU runs without any intervention of thermal
supervision (all four processors have a T
J
UNCTION
from 100°C). When operated above the corresponding curve, various
thermal protection mechanisms may take effect resulting in temporarily reduced CPU performance or finally in an
emergency stop (the CPU is at 130°C) in order to protect the CPU from thermal destruction (in this case the power
must be switched off and then on again). In real applications this means that the board can be operated temporarily
at a higher ambient temperature or at a reduced flow rate and still provide some margin for temporarily requested
peak performance before thermal protection will be activated.
An airflow of 2.0 m/s to 3.0 m/s or a volumetric flow rate of 15 CFM to 20 CFM is a typical value for a standard
Kontron ASM rack. For other racks or housings the available airflow will differ. The maximum ambient operating
temperature must be determined for such environments.
How to read the diagram in Figures 7 and 9
Select a specific CPU and choose a specific working point. For a given flow rate there is a maximum airflow input
temperature (= ambient temperature) provided. Below this operating point, thermal supervision will not be activated.
Above this operating point, thermal supervision will become active protecting the CPU from thermal destruction. The
minimum airflow rate provided must be more than the value specified in the diagram.
How to read the diagram in Figure 8
Select a specific working point. For a given CPU frequency there is a maximum airflow input temperature (= ambient
temperature) provided. Below this operating point, thermal supervision will not be activated. Above this operating
point, thermal supervision will become active by reducing the CPU frequency to protect the CPU from thermal
destruction. The minimum airflow rate provided must be more than the value specified in the diagram.
Volumetric flow rate
The volumetric flow rate refers to an airflow through a fixed cross-sectional area (i.e. slot width x depth. The
volumetric flow rate is specified in m³/h (cubic-meter-per-hour) or cfm (cubic-feet-per-minute) respectively.
Conversion: 1 cfm = 1.7 m³/h; 1 m³/h = 0.59 cfm
Airflow
At a given cross-sectional area and a required flow rate, an average, homogeneous airflow speed can be calculated
using the following formula:
Airflow = Volumetric flow rate / area.
The airflow is specified in m/s (meter-per-second) or in fps (feet-per-second) respectively.
Conversion: 1 fps = 0.3048 m/s; 1 m/s = 3.28 fps
The following figures illustrate the thermal operational limits of the CP3005-SA taking into consideration power
consumption vs. ambient air temperature vs. airflow rate.
The CP3005-SA must be operated within the thermal operational limits indicated below.
