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MC9S08GB60A Datasheet, PDF (262/302 Pages) Freescale Semiconductor, Inc – HCS08 Microcontrollers | |||
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Appendix A Electrical Characteristics
A.3 Thermal Characteristics
This section provides information about operating temperature range, power dissipation, and package
thermal resistance. Power dissipation on I/O pins is usually small compared to the power dissipation in
on-chip logic and voltage regulator circuits and it is user-determined rather than being controlled by the
MCU design. In order to take PI/O into account in power calculations, determine the difference between
actual pin voltage and VSS or VDD and multiply by the pin current for each I/O pin. Except in cases of
unusually high pin current (heavy loads), the difference between pin voltage and VSS or VDD will be very
small.
Table A-2. Thermal Characteristics
Rating
Symbol
Value
Unit
Temp.
Code
Operating temperature range (packaged)
TA
â40 to 85
°C
C
Thermal resistance
64-pin LQFP (GBxxA)
48-pin QFN (GTxxA)
44-pin QFP (GTxxA)
42-pin SDIP (GTxxA)
θJA1,2
65
82
°C/W
â
118
57
1 Junction temperature is a function of die size, on-chip power dissipation, package thermal resistance,
mounting site (board) temperature, ambient temperature, airflow, power dissipation of other components
on the board, and board thermal resistance.
2 Per SEMI G38-87 and JEDEC JESD51-2 with the single layer board horizontal. Single layer board is
designed per JEDEC JESD51-3.
The average chip-junction temperature (TJ) in °C can be obtained from:
TJ = TA + (PD à θJA)
Eqn. A-1
where:
TA = Ambient temperature, °C
θJA = Package thermal resistance, junction-to-ambient, °C/W
PD = Pint + PI/O
Pint = IDD Ã VDD, Watts â chip internal power
PI/O = Power dissipation on input and output pins â user determined
For most applications, PI/O << Pint and can be neglected. An approximate relationship between PD and TJ
(if PI/O is neglected) is:
PD = K ÷ (TJ + 273°C)
Solving equations 1 and 2 for K gives:
Eqn. A-2
K = PD à (TA + 273°C) + θJA à (PD)2
Eqn. A-3
where K is a constant pertaining to the particular part. K can be determined from equation 3 by measuring
PD (at equilibrium) for a known TA. Using this value of K, the values of PD and TJ can be obtained by
solving equations 1 and 2 iteratively for any value of TA.
MC9S08GB60A Data Sheet, Rev. 2
262
Freescale Semiconductor
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