MC9S12A128 Datasheet, PDF (62/92 Pages) Motorola, Inc – Microcontroller unit (MCU)

MC9S12A128 Device Guide — V01.01
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]
Two cases with internal voltage regulator enabled and disabled must be considered:
1. Internal Voltage Regulator disabled
PINT = IDD ⋅ VDD + IDDPLL ⋅ VDDPLL + IDDA ⋅ VDDA
∑ ^{PIO =}
RDSON ⋅ IIOi2
i
P_IO is the sum of all output currents on I/O ports associated with V_DDX and V_DDR.
For R_DSON is valid:
respectively
RDSON = ^{V--I--O-O----L-L--;for} outputs driven low
RDSON = -V----D----D----I-5-O----^–-H---V-----O-----H-- ;for outputs driven high
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