Appendix A Electrical Characteristics
MC9S12XE-Family Reference Manual Rev. 1.19
Freescale Semiconductor
1207
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
Two cases with internal voltage regulator enabled and disabled must be considered:
1. Internal voltage regulator disabled
2. Internal voltage regulator enabled
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
IO
R
DSON
i
∑
I
IO
i
2
⋅
=
R
DSON
V
OL
I
OL
------------ for outputs driven low
;
=
R
DSON
V
DD35
V
OH
–
I
OH
--------------------------------------- for outputs driven high
;
=
P
INT
I
DD
V
DD
⋅
I
DDPLL
V
DDPLL
⋅
I
DDA
+
V
DDA
⋅
+
=
P
INT
I
DDR
V
DDR
⋅
I
DDA
V
DDA
⋅
+
=
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:
S12XE
products
in
208
MAPBGA
packages
