Datasheet

Electrical Characteristics
MC9S08QE8 Series Data Sheet, Rev. 8
Freescale Semiconductor 9
The average chip-junction temperature (T
J
) in C can be obtained from:
T
J
= T
A
+ (P
D
 
JA
) Eqn. 1
where:
T
A
= Ambient temperature, C

JA
= Package thermal resistance, junction-to-ambient, C/W
P
D
= P
int
P
I/O
P
int
= I
DD
 V
DD
, Watts — chip internal power
P
I/O
= Power dissipation on input and output pins — user determined
For most applications, P
I/O
 P
int
and can be neglected. An approximate relationship between P
D
and T
J
(if P
I/O
is neglected) is:
P
D
= K  (T
J
+ 273 C) Eqn. 2
Solving Equation 1 and Equation 2 for K gives:
K = P
D
 (T
A
+ 273 C) + 
JA
 (P
D
)
2
Eqn. 3
Table 4. Thermal Characteristics
Rating Symbol Value Unit
Operating temperature range
(packaged)
T
A
T
L
to T
H
–40 to 85
C
Maximum junction temperature T
JM
95 C
Thermal resistance
Single-layer board
32-pin QFN

JA
110
C/W
32-pin LQFP 66
28-pin SOIC 57
20-pin SOIC 71
16-pin PDIP 64
16-pin TSSOP 108
Thermal resistance
Four-layer board
32-pin QFN

JA
42
C/W
32-pin LQFP 47
28-pin SOIC 42
20-pin SOIC 52
16-pin PDIP 47
16-pin TSSOP 78