MC9S08SH8CSC View Datasheet(PDF) - Freescale Semiconductor

Part Name

Description

Manufacturer

MC9S08SH8CSC

HCS08 Microcontrollers

Freescale Semiconductor 

Appendix A Electrical Characteristics

The average chip-junction temperature (TJ) in °C can be obtained from:

where:

TJ = TA + (PD × θJA)

Eqn. A-1

TA = Ambient temperature, °C

θJA = Package thermal resistance, junction-to-ambient, °C/W

PD = Pint + PI/O

Pint = IDD × VDD, Watts — chip internal power

PI/O = Power dissipation on input and output pins — 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 Equation A-1 and Equation A-2 for K gives:

Eqn. A-2

K = PD × (TA + 273°C) + θJA × (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 Equation A-1 and Equation A-2 iteratively for any value of TA.

MC9S08SH8 MCU Series Data Sheet, Rev. 3

292

Freescale Semiconductor

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