Digital Equipment AXPpci 33, Руководство по конструкции

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Environmental Data
Table 3–7 DECchip 21066A (233 MHz) Cooling Using Fan/Heatsink
Fan
Voltage AXPpci 33
CPU Power
T c
Max Theta jc Theta ja Theta ca
Maximum
Ambient
Temperature Notes
12 V 23 W 84°C 0.70°C/W 2.10°C/W 1.30°C/W 54°C 1, 2
Using part number 12–35739–34 for heatsink and specified fan.
Notes:
1 If the recommended thermal pad (thermal interface between the 21066A and heatsink) is not used, the Theta
jc and Theta ja values will increase by 0.45°C/W. The end result is a decrease in maximum allowable ambient
temperature by 10.4°C.
2 Operation above 40°C ambient temperature requires further thermal analysis by the system integrator. This
ensures that maximum operating temperatures are not exceeded for any other device including storage devices,
power supplies, PCI or ISA option modules, or other chips on the MLB.
3.1.2.3 DECchip 21068 (66 MHz) Cooling Requirements
Tables 3–8 through 3–10 list the DECchip 21068 (66 MHz) cooling
requirements using a low-profile heatsink, high-profile heatsink, and
fan/heatsink, respectively.
Table 3–8 DECchip 21068 (66 MHz) Cooling Using Low-Profile Heatsink
Air
Velocity
LFM
AXPpci 33
CPU Power
T c
Max Theta jc Theta ja Theta ca
Maximum
Ambient
Temperature Notes
100 9W 93°C 0.70°C/W 7.25°C/W 6.55°C/W 34°C 1
200 9W 93°C 0.70°C/W 5.70°C/W 5.00°C/W 48°C 1
400 9W 93°C 0.70°C/W 3.80°C/W 3.10°C/W 65°C 1, 2
600 9W 93°C 0.70°C/W 2.80°C/W 2.10°C/W 74°C 1, 2
800 9W 93°C 0.70°C/W 2.35°C/W 1.65°C/W 78°C 1, 2
1,000 9W 93°C 0.70°C/W 2.10°C/W 1.40°C/W 80°C 1, 2
Using part number 12–35739–18 low-profile heatsink.
Notes:
1 If the recommended thermal pad (thermal interface between the 21068 and heatsink) is not used, the Theta jc
and Theta ja values will increase by 0.45°C/W. The end result will be a decrease in maximum allowable ambient
temperature by 4°C.
2 Operation above 40°C ambient temperature will require further thermal analysis by the system integrator. This
ensures that maximum operating temperatures are not exceeded for any other device including storage devices,
power supplies, PCI or ISA option modules, or other chips on the MLB.
3–5