P R E L I M I N A R Y
THERMAL CHARACTERISTICS
TQFP Package
The variable P is power in watts. Typical power
supply current (ICC) for the Am186EM and Am188EM
microcontrollers is 5.9 mA per MHz of clock frequency.
The Am186EM and Am188EM microcontrollers are
specified for operation with case temperature ranges
from 0°C to +100°C for a commercial temperature de-
vice. Case temperature is measured at the top center
of the package as shown in Figure 15. The various tem-
peratures and thermal resistances can be determined
using the equations in Figure 16 with information given
in Table 8.
θJA
θCA
TC
θJC
θJA is the sum of θJC and θCA. θJC is the internal ther-
mal resistance of the assembly. θCA is the case to am-
bient thermal resistance.
θJA = θJC + θCA
Figure 15. Thermal Resistance(°C/Watt)
θJA = θJC + θCA
P=5.9 mA freq (MHz) VCC
TJ=TC+( P θJC
TJ=TA+ (P θJA
)
)
TC=TJ–( P θJC
)
TC=TA+( P θCA
)
TA=TJ–( P θJA
)
TA=TC–( P θCA
)
Figure 16. Thermal Characteristics Equations
Table 8. Thermal Characteristics (°C/Watt)
Airflow
(Linear Feet
per Minute)
θJC
θCA
θJA
Package/Board
0 fpm
7
7
38
32
28
26
46
36
30
28
18
16
14
12
24
22
20
18
45
39
35
33
56
46
40
38
23
21
19
17
30
28
26
24
200 fpm
400 fpm
600 fpm
0 fpm
PQFP/2-Layer
7
7
10
10
10
10
5
200 fpm
400 fpm
600 fpm
0 fpm
TQFP/2-Layer
200 fpm
400 fpm
600 fpm
0 fpm
5
PQFP/4-Layer
to 6-Layer
5
5
6
200 fpm
400 fpm
600 fpm
6
TQFP/4-Layer
to 6-Layer
6
6
54
Am186/188EM and Am186/188EMLV Microcontrollers
AMD [ AMD ]
