Motorola MC68020 User Manual page 278

Table 10-1. θ
Maximum
Typical
*
Natural convection
Table 10-2 shows the relationship between clock speed and power dissipation for any
package type. The worst case operating conditions are used for thermal management
design, while typical values are used for reliability analysis.
Rated Frequency (MHz)
Table 10-3 shows the relationship between board temperature rise and power dissipation
in the test environment for the CQFP package. Derate θ
in the application by adding (0.8/P
table. Board temperature was measured on the top surface of the board directly under the
device.
Values for thermal resistance presented in this document were derived using the
procedure described in Motorola Reliability Report 7843, "Thermal Resistance
Measurement Method for MC68XX Microcomponent Devices," and are provided for
design purposes only. Thermal measurements are complex and dependent on procedure
and setup. User-derived values for thermal resistance may differ.
MOTOROLA
vs. Airflow—MC68020 CQFP Package
JA
θ
JA
No Heatsink
With Heatsink
No Heatsink
With Heatsink
Table 10-2. Power vs. Rated Frequency
(at T Maximum = 110°C)
J
P
33
25
20
16
) * [T
D
Table 10-3. Temperature Rise of Board vs. P
—MC68020 CQFP Package
Natural Convection
T (°C)—No Heatsink
ba
M68020 USER'S MANUAL
Airflow in Linear Feet/Minute
*
0 200
46 28
35 20
43 25
32 17
Maximum (Watts)
D
1.4
1.2
1.0
0.9
JA
– T
ba(application) ba(table)
P
D
0.6W 1.0W
18 27
500
24
18
21
15
P Typical (Watts)
D
0.84
0.72
0.60
0.54
based on measurements made
] to the θ
values in the
JA
D
1.75W
53
10-3