Datasheet

Appendix A Electrical Characteristics
652 MC9S12C-Family / MC9S12GC-Family Freescale Semiconductor
Rev 01.24
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:
Two cases with internal voltage regulator enabled and disabled must be considered:
1. Internal Voltage Regulator disabled
Which is the sum of all output currents on I/O ports associated with V
DDX
and V
DDM
.
For R
DSON
is valid:
respectively
2. Internal voltage regulator enabled
I
DDR
is the current shown in Table A-8 and not the overall current flowing into VDDR, which
additionally contains the current flowing into the external loads with output high.
Which is the sum of all output currents on I/O ports associated with V
DDX
and V
DDR
.
T
J
T
A
P
D
Θ
JA
•()+=
T
J
Junction Temperature, [°C ]=
T
A
Ambient Temperature, [°C ]=
P
D
Total Chip Power Dissipation, [W]=
Θ
JA
Package Thermal Resistance, [°C/W]=
P
D
P
INT
P
IO
+=
P
INT
Chip Internal Power Dissipation, [W]=
P
INT
I
DD
V
DD
⋅ I
DDPLL
V
DDPLL
⋅ I
DDA
+V
DDA
⋅+=
P
IO
R
DSON
i
∑
I
IO
i
2
⋅=
R
DSON
V
OL
I
OL
------------ for outputs driven low;=
R
DSON
V
DD5
V
OH
–
I
OH
------------------------------------ for outputs driven high;=
P
INT
I
DDR
V
DDR
⋅ I
DDA
V
DDA
⋅+=
P
IO
R
DSON
i
∑
I
IO
i
2
⋅=