AM186ED Datasheet, PDF (52/88 Pages) Advanced Micro Devices – High Performance, 80C186- and 80C188-Compatible, 16-Bit Embedded Microcontrollers

PRELIMINARY
Typical Ambient Temperatures
Table 13. Junction Temperature Calculation
The typical ambient temperature specifications are
based on the following assumptions and calculations:
The commercial operating range of the Am186ED
microcontroller is a case temperature T_C of 0 to 100
degrees Centigrade. T_C is measured at the top center
of the package. An increase in the ambient temperature
causes a proportional increase in T_C.
Microcontrollers up to 40 MHz are specified as 5.0 V
plus or minus 10%. Therefore, 5.0 V is used for
calculating typical power consumption up to 40 MHz.
Typical power supply current (I_CC) in normal usage is
estimated at 5.9 mA per MHz of microcontroller clock
rate.
Speed/
Pkg/
Board
40/P2
40/T2
40/P4-6
40/T4-6
33/P2
33/T2
33/P4-6
33/T4-6
25/P2
T_J(°C)
108.3
111.8
105.9
107.1
106.8
109.7
104.9
105.8
105.2
⋅ T_J = T_{C +} (P θ_JC)
T_C
P
θ_JC
100
1.2
7
100
1.2
10
100
1.2
5
100
1.2
6
100
1.0
7
100
1.0
10
100
1.0
5
100
1.0
6
100
0.7
7
Typical power consumption (watts) = (5.9 mA/MHz)
25/T2
107.4
100
0.7
10
times microcontroller clock rate times V_CC divided by
1000.
Table 12 shows the variables that are used to calculate
the typical power consumption value for each version
of the Am186ED microcontroller.
T _{Table 12. Typical Power Consumption Calculation}
F _{⋅ ⋅ P = MHz ICC VCC/1000}
MHz
Typical I_CC
Volts
40
5.9
5.0
33
5.9
5.0
A ₂₅
5.9
5.0
20
5.9
5.0
Typical
Power (P) in
Watts
1.2
1.0
0.7
0.6
Thermal resistance is a measure of the ability of a
R ^{package to remove heat from a semiconductor device.}
A safe operating range for the device can be calculated
using the formulas from Figure 14 and the variables in
Table 11.
By using the maximum case rating T_C, the typical
D _{power consumption value from Table 12, and θJC from}
Table 11, the junction temperature T_J can be calculated
by using the following formula from Figure 14.
25/P4-6
103.7
100
0.7
5
25/T4-6
104.4
100
0.7
6
20/P2
104.1
100
0.6
7
20/T2
105.9
100
0.6
10
20/P4-6
103.0
100
0.6
5
20/T4-6
103.5
100
0.6
6
By using T_J from Table 13, the typical power
consumption value from Table 12, and a θ_JA value from
Table 11, the typical ambient temperature T_A can be
calculated using the following formula from Figure 14:
T_A = T_J – (P ⋅ θ_JA)
For example, T_A for a 40-MHz PQFP design with a 2-
layer board and 0 fpm airflow is calculated as follows:
T_A = 108.3 – (1.2 ⋅ 45)
T_A = 55.2
In this calculation, T_J comes from Table 13, P comes
from Table 12, and θ_JA comes from Table 11. See Table
14.
T_A for a 33-MHz TQFP design with a 4-layer to 6-layer
board and 200 fpm airflow is calculated as follows:
T_A = 105.8 – (1.0 ⋅ 28)
T_A = 78.6
See Table 17 for the result of this calculation.
T_J = T_C + (P ⋅ θ_JC)
Table 13 shows T_J values for the various versions of
the Am186ED microcontroller. The column titled
Speed/Pkg/Board in Table 13 indicates the clock speed
in MHz, the type of package (P for PQFP and T for
TQFP), and the type of board (2 for 2-layer and 4-6 for
4-layer to 6-layer).
Table 14 through Table 17 and Figure 15 through
Figure 18 show T_A based on the preceding
assumptions and calculations for a range of θ_JA values
with airflow from 0 linear feet per minute to 600 linear
feet per minute.
52
Am186ED/EDLV Microcontrollers