NXP Semiconductors MC9S12G - A.1.8 Power Dissipation and Thermal Characteristics

Electrical Characteristics
MC9S12G Family Reference Manual Rev.1.27
NXP Semiconductors 1183
A.1.8 Power Dissipation and Thermal Characteristics
Power dissipation and thermal characteristics are closely related. The user must assure that the maximum
operating junction temperature is not exceeded. The average chip-junction temperature (T
J
) in C can be
obtained from:
The total power dissipation can be calculated from:
P
IO
is the sum of all output currents on I/O ports associated with V
DDX
, whereby
T
J
T
A
P
D

JA
+=
T
J
Junction Temperature, [C =
T
A
Ambient Temperature, [C =
P
D
Total Chip Power Dissipation, [W]=

JA
Package Thermal Resistance, [C/W]=
P
D
P
INT
P
IO
+=
P
INT
Chip Internal Power Dissipation, [W]=
P
IO
R
DSON
i

I
IO
i
2
=
R
DSON
V
OL
I
OL
------------ f o r o u t p u t s d r i v e n l o w;=
R
DSON
V
DD35
V
OH
–
I
OH
--------------------------------------- f o r o u t p u t s d r i v e n h i g h;=
P
INT
I
DDR
V
DDR
 I
DDA
V
DDA
+=