AM186EM Datasheet, PDF (55/98 Pages) List of Unclassifed Manufacturers – MICROCONTROLLER BLOCK DIAGRAM

PRELIMINARY
Typical Ambient Temperatures
The typical ambient temperature specifications are
based on the following assumptions and calculations:
The commercial operating range of the Am186EM and
Am188EM 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 tem-
perature causes a proportional increase in T_C.
The 40-MHz microcontroller is specified as 5.0 V, plus
or minus 5%. Therefore, 5.25 V is used for calculating
typical power consumption on the 40-MHz microcon-
troller.
Microcontrollers up to 33 MHz are specified as 5.0 V,
plus or minus 10%. Therefore, 5.5 V is used for calcu-
lating typical power consumption up to 33 MHz.
Typical power supply current (I_CC) in normal usage is es-
timated at 5.9 mA per MHz of microcontroller clock rate.
Typical power consumption (watts) = (5.9 mA/MHz)
times microcontroller clock rate times voltage divided
by 1000.
Table 9 shows the variables that are used to calculate
the typical power consumption value for each version
of the Am186EM and Am188EM microcontrollers.
Table 9. Typical Power Consumption
Calculation
P = MHz ⋅ I_CC ⋅ Volts / 1000
MHz
40
Typical I_CC
5.9
Volts
5.25
Typical
Power (P) in
Watts
1.239
33
5.9
5.5
1.07085
25
5.9
5.5
0.81125
20
5.9
5.5
0.649
Thermal resistance is a measure of the ability of a
package to remove heat from a semiconductor device.
A safe operating range for the device can be calculated
using the following formulas from Figure 16 and the
variables in Table 8.
By using the maximum case rating T_C, the typical
power consumption value from Table 9, and θ_JC from
Table 8, the junction temperature T_J can be calculated
by using the following formula from Figure 16.
T_J = T_C + ( P ⋅ θ_JC )
Table 10 shows T_J values for the various versions of the
Am186EM and Am188EM microcontrollers. The column
titled Speed/Pkg/Board in Table 10 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 10.
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
25/T2
25/P4–6
25/T4–6
20/P2
20/T2
20/P4–6
20/T4–6
Junction Temperature Calculation
⋅ T_J = T_{C +} ( P θ_JC )
T_C
P
θ_JC
100
1.239
7
100
1.239
10
100
1.239
5
100
1.239
6
100 1.07085
7
100 1.07085
10
100 1.07085
5
100 1.07085
6
100 0.81125
7
100 0.81125
10
100 0.81125
5
100 0.81125
6
100
0.649
7
100
0.649
10
100
0.649
5
100
0.649
6
T_J
108.7
112.4
106.2
107.4
107.5
110.7
105.3
106.4
105.7
108.1
104.1
104.9
104.5
106.5
103.2
103.9
By using T_J from Table 10, the typical power consumption
value from Table 9, and a θ_JA value from Table 8, the typ-
ical ambient temperature T_A can be calculated using the
following formula from Figure 16.
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 = 108.673 – ( 1.239 ⋅ 45 )
T_A = 52.918
In this calculation, T_J comes from Table 10, P comes
from Table 9, and θ_JA comes from Table 8. See Table 11.
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 = 106.4251 – ( 1.07085 ⋅ 28 )
T_A = 76.4413
See Table 14 for the result of this calculation.
Table 11 through Table 14 and Figure 17 through Fig-
ure 20 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.
Am186/188EM and Am186/188EMLV Microcontrollers
55