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MOTOROLA M68040 USER’S MANUAL 11-21
HEAT SINK
PIN GRID 
ARRAY
SPRING
FRAME
µ MC68040RC25
Figure 11-11. Heat Sink with Attachment
In the specification provided by Thermalloy, Inc., a chart illustrates the heat-sink
temperature rise above ambient versus heat dissipated. This chart applies if no airflow is
used with the heat-sink. Table 11-5 lists the calculations based on this chart.
Table 11-5. Thermal Parameters with Heat Sink and No Airflow
Thermal Mgmt.
Technique Defined Parameters Heat-Sink
Spec. Calculated
MHz Airflow Velocity PDTJθJC TC–T ATCTA
MC68040
25 0 6.3 W 110 °C3 °C/W 64.4 °C 91.1 °C 26.7 °C
25 0 6.6 W 110 °C3 °C/W 66.8 °C 90.2 °C 23.4 °C
25 0 8.6 W 110 °C3 °C/W 82.8 °C 84.2 °C 1.4 °C
33 0 7.7 W 110 °C3 °C/W 75.6 °C 86.9 °C 11.3 °C
33 0 8.0 W 110 °C3 °C/W 78.0 °C 86.0 °C 8.0 °C
33 0 10.0 W 110 °C3 °C/W 94.0 °C 80.0 °C –14.0 °C
MC68LC040 and MC68EC040
20 0 4.0 W 110 °C3 °C/W 45.0 °C 98.0 °C 53.0 °C
25 0 5.0 W 110 °C3 °C/W 54.0 °C 95.0 °C 41.0 °C
33 0 6.3 W 110 °C3 °C/W 64.4 °C 91.1 °C 26.7 °C
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