AM186EM-33VCSLASHW datasheet(55/98 Pages) AMD

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Am186/188EM and Am186/188EMLV Microcontrollers

P R E L IMINAR Y

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 TC of

0 to 100 degrees Centigrade. TC is measured at the top

center of the package. An increase in the ambient tem-

perature causes a proportional increase in TC.

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 (ICC) 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

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 TC, the typical

power consumption value from Table 9, and

JC from

Table 8, the junction temperature TJ can be calculated

by using the following formula from Figure 16.

TJ = TC + ( P

⋅ θ

JC )

Table 10 shows TJ 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.

Junction Temperature Calculation

By using TJ from Table 10, the typical power consumption

value from Table 9, and a

JA value from Table 8, the typ-

ical ambient temperature TA can be calculated using the

following formula from Figure 16.

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:

TA = 108.673 – ( 1.239 ⋅ 45 )

TA = 52.918

In this calculation, TJ comes from Table 10, P comes

from Table 9, and

JA comes from Table 8. See Table 11.

TA for a 33-MHz TQFP design with a 4-layer to 6-layer

board and 200 fpm airflow is calculated as follows:

TA = 106.4251 – ( 1.07085 ⋅ 28 )

TA = 76.4413

See Table 14 for the result of this calculation.

Table 11 through Table 14 and Figure 17 through Fig-

ure 20 show TA based on the preceding assumptions and

calculations for a range of

JA values with airflow from 0

linear feet per minute to 600 linear feet per minute.

P = MHz

⋅ I

⋅ Volts / 1000

Typical

Power (P) in

Watts

MHz

Typical ICC

Volts

5.9

5.25

1.239

5.9

5.5

1.07085

5.9

5.5

0.81125

5.9

5.5

0.649

Speed/

Pkg/

Board

TJ = TC + ( P

⋅ θ

JC )

40/P2

100

1.239

108.7

40/T2

100

1.239

112.4

40/P4–6

100

1.239

106.2

40/T4–6

100

1.239

107.4

33/P2

100

1.07085

107.5

33/T2

100

1.07085

110.7

33/P4–6

100

1.07085

105.3

33/T4–6

100

1.07085

106.4

25/P2

100

0.81125

105.7

25/T2

100

0.81125

108.1

25/P4–6

100

0.81125

104.1

25/T4–6

100

0.81125

104.9

20/P2

100

0.649

104.5

20/T2

100

0.649

106.5

20/P4–6

100

0.649

103.2

20/T4–6

100

0.649

103.9

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