Intel 80386

PHYSICAL DESIGN AND DEBUGGING
GOOD
BAD BAD
G30107
Figure 11-9. CLK2 Loading
WAVEFORMS
GOOD
5V
OV
G30107
Figure 11-10. CLK2 Waveforms
Case temperature calculations offer several advantages over ambient temperature
calculations:
• Case temperature is easier to measure accurately than ambient temperature because the
measurement
is localized to a single point (top center of the package).
o The worst-case junction temperature (T) is lower when calculated with case temperature
for the following reasons:
- The junction-to-case thermal coefficient
(Ojc) is lower than the junction-to-ambient
thermal coefficient
(OJ.); therefore, calculated junction temperature varies less with
power dissipation
(PD).
- Ojc is not affected by air flow in the system; Oja varies with air flow.
11-9