Datasheet

Electrical Specifications
Tables of Data
MC68HC912DT128A — Rev 4.0 Technical Data
MOTOROLA Electrical Specifications 423
Table 21-2. Thermal Characteristics
Characteristic Symbol Value Unit
Average junction temperature
T
J
T
A
+ (P
D
× Θ
JA
)
°C
Ambient temperature
T
A
User-determined °C
Package thermal resistance (junction-to-ambient)
112-pin quad flat pack (QFP)
Θ
JA
40 °C/W
Total power dissipation
(1)
P
D
P
INT
+ P
I/O
or
W
Device internal power dissipation
P
INT
I
DD
× V
DD
W
I/O pin power dissipation
(2)
P
I/O
User-determined W
A constant
(3)
K
P
D
× (T
A
+ 273°C) + Θ
JA
× P
D
2
W · °C
1. This is an approximate value, neglecting P
I/O
.
2. For most applications P
I/O
« P
INT
and can be neglected.
3. K is a constant pertaining to the device. Solve for K with a known T
A
and a measured P
D
(at equilibrium). Use this value of
K to solve for P
D
and T
J
iteratively for any value of T
A
.
K
T
J
273°C+
--------------------------
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cale Semiconductor,
I
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