Compatible Systems RISC 2800i Manual de usuario descargar pdf (Pagina 46)

MPC7448 RISC Microprocessor Hardware Specifications, Rev. 4

46 Freescale Semiconductor

System Design Information

9.7 Power and Thermal Management Information

This section provides thermal management information for the high coefficient of thermal expansion

(HCTE) package for air-cooled applications. Proper thermal control design is primarily dependent on the

system-level design—the heat sink, airflow, and thermal interface material. The MPC7448 implements

several features designed to assist with thermal management, including DFS and the temperature diode.

DFS reduces the power consumption of the device by reducing the core frequency; see Section 9.7.5.1,

“Power Consumption with DFS Enabled,” for specific information regarding power reduction and DFS.

The temperature diode allows an external device to monitor the die temperature in order to detect excessive

temperature conditions and alert the system; see Section 9.7.4, “Temperature Diode,” for more

information.

To reduce the die-junction temperature, heat sinks may be attached to the package by several

methods—spring clip to holes in the printed-circuit board or package, and mounting clip and screw

assembly (see Figure 22); however, due to the potential large mass of the heat sink, attachment through the

printed-circuit board is suggested. In any implementation of a heat sink solution, the force on the die

should not exceed ten pounds (45 Newtons).

Figure 22. BGA Package Exploded Cross-Sectional View with Several Heat Sink Options

NOTE

A clip on heat sink is not recommended for LGA because there may not be

adequate clearance between the device and the circuit board. A through-hole

solution is recommended, as shown in Figure 23.

Thermal

Heat Sink

HCTE BGA Package

Heat Sink

Clip

Printed-Circuit Board

Interface Material

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Compatible Systems RISC 2800i Manual de usuario Pagina 46