MPC750ECSLASHD datasheet(40/44 Pages) NXP

40 / 44 page

MPC750A RISC Microprocessor Hardware Speciﬁcations

System Design Information

The following section provides a heat sink selection example using one of the commercially available heat

sinks.

1.8.7.3 Heat Sink Selection Example

For preliminary heat sink sizing, the die-junction temperature can be expressed as follows:

Tj = Ta + Tr + (θjc + θint + θsa) * Pd

Where:

Tj is the die-junction temperature

Ta is the inlet cabinet ambient temperature

Tr is the air temperature rise within the computer cabinet

jc is the junction-to-case thermal resistance

int is the adhesive or interface material thermal resistance

sa is the heat sink base-to-ambient thermal resistance

Pd is the power dissipated by the device

During operation the die-junction temperatures (Tj) should be maintained less than the value speciﬁed in

Table 3. The temperature of the air cooling the component greatly depends upon the ambient inlet air

temperature and the air temperature rise within the electronic cabinet. An electronic cabinet inlet-air

temperature (Ta) may range from 30 to 40 °C. The air temperature rise within a cabinet (Tr) may be in the

range of 5 to 10 °C. The thermal resistance of the thermal interface material (

int) is typically about 1

°C/W. Assuming a Ta of 30 °C, a Tr of 5 °C, a CQFP package θjc = 2.2, and a power consumption (Pd) of

4.5 watts, the following expression for Tj is obtained:

Die-junction temperature: Tj = 30 °C + 5 °C + (2.2 °C/W + 1.0 °C/W + θsa) * 4.5 W

For a Thermalloy heat sink #2328B, the heat sink-to-ambient thermal resistance (

sa) versus airﬂow

velocity is shown in Figure 23.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

IVE

D B

Y F

INC

MPC750EC/D bảng dữ liệu(PDF) 40 Page - NXP Semiconductors