MC68HC705C Motorola, MC68HC705C Datasheet - Page 172

• Manufacturer Part Number: MC68HC705C
• Description: HCMOS Microcontroller Unit
• Manufacturer: Motorola

Electrical Specifications
13.6 Power Considerations
Technical Data
172
The average chip junction temperature, T
Where:
For most applications, P
Ignoring P
Solving equations (1) and (2) for K gives:
where K is a constant pertaining to the particular part. K can be
determined from equation (3) by measuring P
known T
by solving equations (1) and (2) iteratively for any value of T
T
P
P
P
JA
A
D
INT
I/O
= ambient temperature in C
= P
= package thermal resistance, junction to ambient in C/W
= power dissipation on input and output pins (user-determined)
A
= I
. Using this value of K, the values of P
INT
I/O
CC
, the relationship between P
= P
+ P
Electrical Specifications
V
D
I/O
CC
x (T
T
= chip internal power dissipation
P
J
D
A
= T
I/O
+ 273 C) +
=
A
< P
T
+ (P
J
INT
+ 273 C
D
K
and can be neglected.
x
JA
JA
)
x (P
D
J
, in C can be obtained from:
and T
D
D
)
D
2
MC68HC705C8A — Rev. 2.0
(at equilibrium) for a
and T
J
is approximately:
J
can be obtained
A
MOTOROLA
.
(1)
(2)
(3)