MPC750EC datasheet(41/44 Pages) NXP

41 / 44 page

MPC750A RISC Microprocessor Hardware Speciﬁcations

System Design Information

Figure 23. Thermalloy #2328B Heat Sink-to-Ambient Thermal Resistance Versus Airflow Velocity

Assuming an air velocity of 0.5 m/s, we have an effective Rsa of 7 °C/W, thus

Tj = 30 °C + 5 °C + (2.2 °C/W +1.0 °C/W + 7 °C/W) * 4.5 W,

resulting in a die-junction temperature of approximately 81 °C which is well within the maximum

operating temperature of the component.

Other heat sinks offered by Chip Coolers, IERC, Thermalloy, Wakeﬁeld Engineering, and Aavid

Engineering offer different heat sink-to-ambient thermal resistances, and may or may not need air ﬂow.

Though the die junction-to-ambient and the heat sink-to-ambient thermal resistances are a common

ﬁgure-of-merit used for comparing the thermal performance of various microelectronic packaging

technologies, one should exercise caution when only using this metric in determining thermal management

because no single parameter can adequately describe three-dimensional heat ﬂow. The ﬁnal die-junction

operating temperature, is not only a function of the component-level thermal resistance, but the

system-level design and its operating conditions. In addition to the component's power consumption, a

number of factors affect the ﬁnal operating die-junction temperature—airﬂow, board population (local heat

ﬂux of adjacent components), heat sink efﬁciency, heat sink attach, heat sink placement, next-level

interconnect technology, system air temperature rise, altitude, etc.

Due to the complexity and the many variations of system-level boundary conditions for today's

microelectronic equipment, the combined effects of the heat transfer mechanisms (radiation, convection

and conduction) may vary widely. For these reasons, we recommend using conjugate heat transfer models

for the board, as well as, system-level designs.

To expedite system-level thermal analysis, several

“compact” thermal-package models are available within FLOTHERM®.

These are available upon

request.

0.5

1.5

2.5

3.5

Thermalloy #2328B Pin-fin Heat Sink

Approach Air Velocity (m/s)

(25 x28 x 15 mm)

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

IVE

D B

Y F

INC

MPC750EC Datasheet(PDF) 41 Page - NXP Semiconductors