MC9S08LL16_10 Datasheet, PDF(11/44 Page) Freescale Semiconductor, Inc

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MC9S08LL16_10 Datasheet, PDF (11/44 Pages) Freescale Semiconductor, Inc – MC9S08LL16 Series

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Electrical Characteristics

3.4 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. 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 5. Thermal Characteristics

Rating

Operating temperature range

(packaged)

Maximum junction temperature

Thermal resistance

Single-layer board

64-pin LQFP

48-pin QFN

48-pin LQFP

Thermal resistance

Four-layer board

64-pin LQFP

48-pin QFN

48-pin LQFP

Symbol

TJM

ï±JA

Value

Unit

TL to TH

â40 to 85

ï°C

ï°C/W

ï±JA

ï°C/W

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

where:

TJ = TA + (PD ï´ ï±JA)

Eqn. 3-1

TA = Ambient temperature, ï°C

ï±JA = Package thermal resistance, junction-to-ambient, ï°C/W

PD = Pint ï«ï PI/O

Pint = IDD ï´ VDD, Watts â chip internal power

PI/O = Power dissipation on input and output pins â user determined

For most applications, PI/O ï¼ï¼ Pint and can be neglected. An approximate relationship between PD and TJ

(if PI/O is neglected) is:

PD = K ï¸ (TJ + 273ï°C)

Solving Equation 3-1 and Equation 3-2 for K gives:

Eqn. 3-2

K = PD ï´ (TA + 273ï°C) + ï±JA ï´ (PD)2

Eqn. 3-3

MC9S08LL16 Series MCU Data Sheet, Rev. 6

Freescale Semiconductor

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