AM186 Datasheet, PDF (62/112 Pages) Advanced Micro Devices – High-Performance, 80C186- and 80C188-Compatible, 16-Bit Embedded Microcontrollers with RAM

Typical Ambient Temperatures
Table 12. Junction Temperature Calculation
The typical ambient temperature specifications are
based on the following assumptions and calculations:
The commercial operating range of the Am186ER and
Am188ER microcontrollers 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.
The 50-MHz microcontroller is specified as 3.3 V, plus
or minus 10%. Therefore, 3.6 V is used for calculating
typical power consumption on the 50-MHz
microcontroller.
Typical power supply current (I_CC) in normal usage is
estimated at 3.7 mA per MHz of microcontroller clock
rate.
Speed/
Pkg/
Board
50/P2
50/T2
50/P4–6
50/T4–6
40/P2
40/T2
40/P4–6
40/T4–6
33/P2
33/T2
⋅ T_J = T_C + (P θ_JC)
T_C
P
θ_JC
100
0.662
7
100
0.662
10
100
0.662
5
100
0.662
6
100
0.522
7
100
0.522
10
100
0.522
5
100
0.522
6
100
0.432
7
100
0.432
10
T_J
104.6
106.6
103.3
104.0
103.7
105.2
102.6
103.1
103.0
104.3
Typical power consumption can be calculated using the
following formula:
(Watts) = (3.7 mA/MHz) ⋅ 50 MHz ⋅ (3.6 V/1000)
Table 11 shows the variables that are used to calculate
the typical power consumption value for each version
of the Am186ER and Am188ER microcontrollers.
T _{Table 11. Typical Power Consumption Calculation}
F P = MHz ⋅ I_CC ⋅ Volts / 1000
MHz
50
Typical I_CC
3.7
Volts
3.6
Typical
Power (P)
in Watts
0.662
40
3.7
3.6
0.522
A ₃₃
3.7
3.6
0.432
25
3.7
3.6
0.342
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 following formulas from Figure 17 and the
variables in Table 10.
D ^{By using the maximum case rating TC, the typical}
33/P4–6
33/T4–6
25/P2
25/T2
25/P4–6
25/T4–6
100
0.432
5
100
0.432
6
100
0.342
7
100
0.342
10
100
0.342
5
100
0.342
6
102.2
102.6
102.4
103.4
101.7
102.1
By using T_J from Table 12, the typical power
consumption value from Table 11, and a θ_JA value from
Table 10, the typical ambient temperature T_A can be
calculated using the following formula from Figure 17.
T_A = T_J – (P ⋅ θ_JA)
For example, T_A for a 50-MHz PQFP design with a
2-layer board and 0 fpm airflow is calculated as follows:
T_A = 104.6 – (0.662 ⋅ 45)
T_A = 74.81
In this calculation, T_J comes from Table 12, P comes
from Table 11, and θ_JA comes from Table 10. See Table
13.
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 = 102.6 – (0.432 ⋅ 28)
power consumption value from Table 11, and θ_JC from
T_A = 90.5
Table 10, the junction temperature T_J can be calculated
by using the following formula from Figure 17.
See Table 16 for the result of this calculation.
T_J = T_C + (P ⋅ θ_JC)
Table 12 shows T_J values for the various versions of the
Am186ER and Am188ER microcontrollers. The
Table 13 through Table 16 and Figure 18 through
Figur e 21 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
Speed/Pkg/Board column in Table 12 indicates the feet per minute.
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).
62
Am186^TMER and Am188^TMER Microcontrollers Data Sheet