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Appendix A Electrical Characteristics
MC9S12XDP512 Data Sheet, Rev. 2.21
1244
Freescale Semiconductor
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 (TJ) 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
PIO is the sum of all output currents on I/O ports associated with VDDX and VDDR.
For RDSON is valid:
respectively
2. Internal voltage regulator enabled
IDDR is the current shown in Table A-10. and not the overall current owing into VDDR, which additionally contains the current owing into the external loads with output high.
PIO is the sum of all output currents on I/O ports associated with VDDX and VDDR.
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
=