MPC5200B_10 datasheet(9/72 Pages) FREESCALE

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MPC5200B Data Sheet, Rev. 4

Freescale Semiconductor

1.1.6

Thermal Characteristics

1.1.6.1

Heat Dissipation

An estimation of the chip-junction temperature, TJ, can be obtained from the following equation:

TJ =TA+(RθJA × PD)

Eqn. 3

where:

TA = ambient temperature for the package (ºC)

RθJA = junction to ambient thermal resistance (ºC/W)

PD = power dissipation in package (W)

The junction to ambient thermal resistance is an industry standard value, which provides a quick and easy estimation of thermal

performance. Unfortunately, there are two values in common usage: the value determined on a single layer board, and the value

obtained on a board with two planes. For packages such as the PBGA, these values can be different by a factor of two. Which

value is correct depends on the power dissipated by other components on the board. The value obtained on a single layer board

is appropriate for the tightly packed printed circuit board. The value obtained on the board with the internal planes is usually

appropriate if the board has low power dissipation and the components are well separated.

Historically, the thermal resistance has frequently been expressed as the sum of a junction to case thermal resistance and a case

to ambient thermal resistance:

Table 7. Thermal Resistance Data

Rating

Board Layers

Sym

Value

Unit

Notes

SpecID

Junction to Ambient

Natural Convection

Single layer board

(1s)

RθJA

°C/W

(1),(2)

1 Junction temperature is a function of die size, on-chip power dissipation, package thermal resistance, mounting site

(board) temperature, ambient temperature, air flow, 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.

D6.1

Junction to Ambient

Natural Convection

Four layer board (2s2p)

RθJMA

°C/W

(1),(3)

3 Per JEDEC JESD51-6 with the board horizontal.

D6.2

Junction to Ambient (@200

ft/min)

Single layer board

(1s)

RθJMA

°C/W

(1),(3)

D6.3

Junction to Ambient (@200

ft/min)

Four layer board

(2s2p)

RθJMA

°C/W

(1),(3)

D6.4

Junction to Board

—

RθJB

°C/W

(4)

4 Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is

measured on the top surface of the board near the package.

D6.5

Junction to Case

—

RθJC

8°C/W

(5)

5 Thermal resistance between the die and the case top surface as measured by the cold plate method (MIL

SPEC-883 Method 1012.1).

D6.6

Junction to Package Top

Natural Convection

2°C/W

(6)

6 Thermal characterization parameter indicating the temperature difference between package top and the junction

temperature per JEDEC JESD51-2. When Greek letters are not available, the thermal characterization parameter

is written as Psi-JT.

D6.7

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