P R E L I M I N A R Y
column titled Speed/Pkg/Board in Table 12 indicates
Typical Ambient Temperatures
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).
The typical ambient temperature specifications are
based on the following assumptions and calculations:
The commercial operating range of the Am186ES and
Am188ES microcontrollers is a case temperature TC of
0 to 100 degrees Centigrade. TC is measured at the top
center of the package. An increase in the ambient
temperature causes a proportional increase in TC.
Table 12. Junction Temperature Calculation
Speed/
TJ = TC + (P θJC
)
Pkg/
Board
TJ
TC
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
P
θJC
7
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
microcontroller.
40/P2
108.673
112.39
1.239
40/T2
1.239
10
5
40/P4-6
40/T4-6
33/P2
106.195
107.434
107.49595
110.7085
105.35425
106.4251
105.67875
108.1125
104.05625
104.8675
104.543
106.49
1.239
Microcontrollers up to 33 MHz are specified as 5.0 V
plus or minus 10%. Therefore, 5.5 V is used for
calculating typical power consumption up to 33 MHz.
1.239
6
1.07085
1.07085
1.07085
1.07085
0.81125
0.81125
0.81125
0.81125
0.649
7
33/T2
10
5
Typical power supply current (ICC) in normal usage is
estimated at 5.9 mA per MHz of microcontroller clock
rate.
33/P4-6
33/T4-6
25/P2
6
7
Typical power consumption (watts) = (5.9 mA/MHz)
times microcontroller clock rate times voltage divided
by 1000.
25/T2
10
5
25/P4-6
25/T4-6
20/P2
6
Table 11 shows the variables that are used to calculate
the typical power consumption value for each version
of the Am186ES and Am188ES microcontrollers.
7
20/T2
0.649
10
5
20/P4-6
20/T4-6
103.245
103.894
0.649
0.649
6
Table 11. Typical Power Consumption
Calculation
Typical
Power (P) in
By using TJ from Table 12, the typical power
consumption value from Table 11, and a θJA value from
Table 10, the typical ambient temperature TA can be
calculated using the following formula from Figure 14:
P = MHz ICC Volts / 1000
Watts
MHz
Typical ICC
Volts
40
33
25
20
5.9
5.9
5.9
5.9
5.25
5.5
1.239
1.07085
0.81125
0.649
TA = TJ – (P θJA)
For example, TA for a 40-MHz PQFP design with a 2-
layer board and 0 fpm airflow is calculated as follows:
5.5
5.5
TA = 108.673 – (1.239 45)
TA = 52.918
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 formulas from Figure 14 and the variables in
Table 10.
In this calculation, TJ comes from Table 12, P comes
from Table 11, and θJA comes from Table 10. See Table
13.
TA for a 33-MHz TQFP design with a 4-layer to 6-layer
board and 200 fpm airflow is calculated as follows:
By using the maximum case rating TC, the typical
power consumption value from Table 11, and θJC from
Table 10, the junction temperature TJ can be
calculated by using the following formula from Figure
14.
TA = 106.4251 – (1.07085 28)
TA = 76.4413
See Table 16 for the result of this calculation.
Table 13 through Table 16 and Figure 15 through
Figure 18 show TA based on the preceding
assumptions and calculations for a range of θJA values
with airflow from 0 linear feet per minute to 600 linear
feet per minute.
TJ = TC + (P θJC
)
Table 12 shows TJ values for the various versions of
the Am186ES and Am188ES microcontrollers. The
56
Am186/188ES and Am186/188ESLV Microcontrollers
AMD [ AMD ]
