MPC885ZP80 datasheet(14/92 Pages) FREESCALE

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MPC885/MPC880 Hardware Specifications, Rev. 3

Freescale Semiconductor

Power Supply and Power Sequencing

7.5 Experimental Determination

To determine the junction temperature of the device in the application after prototypes are available, the thermal

characterization parameter (

ΨJT) can be used to determine the junction temperature with a measurement of the

temperature at the top center of the package case using the following equation:

TJ = TT + (ΨJT × PD)

where:

JT = thermal characterization parameter

TT = thermocouple temperature on top of package

PD = power dissipation in package

The thermal characterization parameter is measured per the JESD51-2 specification published by JEDEC using a 40

gauge type T thermocouple epoxied to the top center of the package case. The thermocouple should be positioned

so that the thermocouple junction rests on the package. A small amount of epoxy is placed over the thermocouple

junction and over about 1 mm of wire extending from the junction. The thermocouple wire is placed flat against the

package case to avoid measurement errors caused by the cooling effects of the thermocouple wire.

7.6 References

Semiconductor Equipment and Materials International

(415) 964-5111

805 East Middlefield Rd

Mountain View, CA 94043

MIL-SPEC and EIA/JESD (JEDEC) specifications

800-854-7179 or

(Available from Global Engineering Documents)

303-397-7956

JEDEC Specifications

http://www.jedec.org

1. C.E. Triplett and B. Joiner, “An Experimental Characterization of a 272 PBGA Within an Automotive Engine

Controller Module,” Proceedings of SemiTherm, San Diego, 1998, pp. 47-54.

2. B. Joiner and V. Adams, “Measurement and Simulation of Junction to Board Thermal Resistance and Its

Application in Thermal Modeling,” Proceedings of SemiTherm, San Diego, 1999, pp. 212-220.

Power Supply and Power Sequencing

This section provides design considerations for the MPC885/880 power supply. The MPC885/880 has a core voltage

(VDDL) and PLL voltage (VDDSYN), which both operate at a lower voltage than the I/O voltage VDDH. The I/O

section of the MPC885/880 is supplied with 3.3 V across VDDH and VSS (GND).

The signals PA[0:15], PB[14:31], PC[4:15], PD[3:15], TDI, TDO, TCK, TRST_B, TMS, MII_TXEN, and

MII_MDIO are 5-V tolerant. All inputs cannot be more than 2.5 V greater than VDDH. In addition, 5-V tolerant pins

can not exceed 5.5 V and remaining input pins cannot exceed 3.465 V. This restriction applies to power up/down

and normal operation.

One consequence of multiple power supplies is that when power is initially applied the voltage rails ramp up at

different rates. The rates depend on the nature of the power supply, the type of load on each power supply, and the

manner in which different voltages are derived. The following restrictions apply:

•VDDL must not exceed VDDH during power up and power down.

•VDDL must not exceed 1.9 V, and VDDH must not exceed 3.465 V.

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