MPC8260EC datasheet(10/41 Pages) FREESCALE

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MPC8260 PowerQUICC II Integrated Communications Processor Hardware Specifications, Rev. 2

Freescale Semiconductor

Electrical and Thermal Characteristics

2.2

Thermal Characteristics

Table 4 describes thermal characteristics.

2.3

Power Considerations

The average chip-junction temperature, TJ, in °C can be obtained from the following:

TJ = TA + (PD x θJA)

(1)

where

TA = ambient temperature °C

JA = package thermal resistance, junction to ambient, °C/W

PD = PINT + PI/O

PINT = IDD x VDD Watts (chip internal power)

PI/O = power dissipation on input and output pins (determined by user)

For most applications PI/O < 0.3 x PINT. If PI/O is neglected, an approximate relationship between PD and

TJ is the following:

PD = K/(TJ + 273° C)

(2)

Solving equations (1) and (2) for K gives:

K = PD x (TA + 273° C) + θJA x PD

(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.

3 Rev C.2 silicon only.

Table 4. Thermal Characteristics

Characteristics

Symbol

Value

Unit

Air Flow

Thermal resistance for TBGA

θJA

13.071

1 Assumes a single layer board with no thermal vias

°C/W

NC2

2 Natural convection

θJA

9.551

°C/W

1 m/s

θJA

10.483

3 Assumes a four layer board

°C/W

θJA

7.783

°C/W

1 m/s

Note:

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