S912XEG128J2MAA Datasheet, PDF (1207/1324 Pages) Freescale Semiconductor, Inc – Microcontrollers

Appendix A Electrical Characteristics
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:
TJ = TA + (PD • Θ_JA)
TJ = Junction Temperature, [°C ]
TA = Ambient Temperature, [°C ]
PD = Total Chip Power Dissipation, [W]
Θ_JA = Package Thermal Resistance, [°C/W]
The total power dissipation can be calculated from:
PD = PINT + PIO
PINT = Chip Internal Power Dissipation, [W]
∑ ^{PIO =} _i ^{RDSON ⋅ IIOi2}
P_IO is the sum of all output currents on I/O ports associated with V_DDX, whereby
RDSON = ^{V--I--O-O----L-L--;for} outputs driven low
RDSON = ^{V-----D----D-----3-I--O5-----H–}-----V----O-----H---;for outputs driven high
Two cases with internal voltage regulator enabled and disabled must be considered:
1. Internal voltage regulator disabled
PINT = IDD ⋅ VDD + IDDPLL ⋅ VDDPLL + IDDA ⋅ VDDA
2. Internal voltage regulator enabled
PINT = IDDR ⋅ VDDR + IDDA ⋅ VDDA
Freescale Semiconductor
MC9S12XE-Family Reference Manual Rev. 1.25
1207