MPC875 datasheet(13/84 Pages) FREESCALE

13 / 84 page

MPC875/MPC870 Hardware Specifications, Rev. 3.0

Freescale Semiconductor

PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE

Power Supply and Power Sequencing

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 MPC875/870 power supply. The MPC875/870 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 MPC875/870 is supplied with 3.3 V across VDDH and VSS (GND).

The signals PA[0:3], PA[8:11], PB15, PB[24:25]; PB[28:31], PC[4:7], PC[12:13], PC15] PD[3:15], TDI,

TDO, TCK, TRST, TMS, MII_TXEN, and MII_MDIO are 5-V tolerant. No input can be more than 2.5 V

greater than VDDH. In addition, 5 V-tolerant pins cannot 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.

These cautions are necessary for the long-term reliability of the part. If they are violated, the electrostatic

discharge (ESD) protection diodes are forward-biased, and excessive current can flow through these diodes.

If the system power supply design does not control the voltage sequencing, the circuit shown in Figure 3

can be added to meet these requirements. The MUR420 Schottky diodes control the maximum potential

difference between the external bus and core power supplies on power up, and the 1N5820 diodes regulate

the maximum potential difference on power down.

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