Motorola M68000 User Manual page 143

Table 10-1 summarizes maximum power dissipation and average junction temperature
for the curve drawn in Figure 10-1, using the minimum and maximum values of ambient
temperature for different packages and substituting J C for J A (assuming good thermal
management). Table 10-2 provides the maximum power dissipation and average junction
temperature assuming that no thermal management is applied (i.e., still air).
Since the power dissipation curve shown in Figure 10-1 is
negatively sloped, power dissipation declines as ambient
temperature increases.
dissipation occurs at the lowest rated ambient temperature, but
the highest average junction temperature occurs at the
maximum ambient temperature where power dissipation is
lowest .
2.2
2.0
1.8
1.6
1.4
1.2
1.0
Figure 10-1. MC68000 Power Dissipation (P D ) vs Ambient Temperature (T A )
(Not Applicable to MC68HC000/68HC001/68EC000)
MOTOROLA M68000 8-/16-/32-BIT MICROPROCESSORS USER'S MANUAL
Freescale Semiconductor, Inc.
NOTE
- 55 - 40
0
AMBIENT TEMPERATURE (T ), C
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Therefore, maximum power
25 70 85
A
110 125
10-3