Appendix A Electrical Characteristics
MC9S12XDP512 Data Sheet, Rev. 2.11
924 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 flowing into VDDR, which
additionally contains the current flowing into the external loads with output high.
PIO is the sum of all output currents on I/O ports associated with VDDX and VDDR.
TJTAPDΘJA
()+=
TJJunction Temperature, [°C]=
TAAmbient Temperature, [°C]=
PDTotal Chip Power Dissipation, [W]=
ΘJA Package Thermal Resistance, [°C/W]=
PDPINT PIO
+=
PINT Chip Internal Power Dissipation, [W]=
PINT IDD VDD
IDDPLL VDDPLL
IDDA
+V
DDA
+=
PIO RDSON
i
IIOi
2
=
RDSON
VOL
IOL
------------ for outputs driven low;=
RDSON
VDD5 VOH
IOH
------------------------------------ for outputs driven high;=
PINT IDDR VDDR
IDDA VDDA
+=
PIO RDSON
i
IIOi
2
=