AM186 datasheet(62/112 Pages) AMD

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Am186TMER and Am188TMER Microcontrollers Data Sheet

DRAF

Typical Ambient Temperatures

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 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.

The 50-MHz microcontroller is specified as 3.3 V, plus

or minus 10%. Therefore, 3.6 V is used for calculating

t y pical po w e r consu mpti on on t he 50- MH z

microcontroller.

Typical power supply current (ICC) in normal usage is

estimated at 3.7 mA per MHz of microcontroller clock

rate.

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.

Table 11.

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 17 and the

variables in Table 10.

By using the maximum case rating TC, the typical

power consumption value from Table 11, and

JC from

Table 10, the junction temperature TJ can be calculated

by using the following formula from Figure 17.

TJ = TC + (P ⋅ θJC)

Table 12 shows TJ values for the various versions of the

Am186ER and Am188ER microcontrollers. The

Speed/Pkg/Board column in Table 12 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 12.

Junction Temperature Calculation

By using TJ from Table 12, the typical power

consumption value from Table 11, and a

JA value from

Table 10, the typical ambient temperature TA can be

calculated using the following formula from Figure 17.

TA = TJ – (P ⋅ θJA)

For example, TA for a 50-MHz PQFP design with a

2-layer board and 0 fpm airflow is calculated as follows:

TA = 104.6 – (0.662 ⋅ 45)

TA = 74.81

In this calculation, TJ comes from Table 12, P comes

from Table 11, and

JA 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:

TA = 102.6 – (0.432 ⋅ 28)

TA = 90.5

See Table 16 for the result of this calculation.

Table 13 through Table 16 and Figure 18 through

Fi g u r e 21 s h ow 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

3.7

3.6

0.662

3.7

3.6

0.522

3.7

3.6

0.432

3.7

3.6

0.342

Speed/

Pkg/

Board

TJ = TC + (P

⋅ θ

JC)

50/P2

100

0.662

104.6

50/T2

100

0.662

106.6

50/P4–6

100

0.662

103.3

50/T4–6

100

0.662

104.0

40/P2

100

0.522

103.7

40/T2

100

0.522

105.2

40/P4–6

100

0.522

102.6

40/T4–6

100

0.522

103.1

33/P2

100

0.432

103.0

33/T2

100

0.432

104.3

33/P4–6

100

0.432

102.2

33/T4–6

100

0.432

102.6

25/P2

100

0.342

102.4

25/T2

100

0.342

103.4

25/P4–6

100

0.342

101.7

25/T4–6

100

0.342

102.1

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