Power Supply and Power Sequencing
7.6 References
Semiconductor Equipment and Materials International
805 East Middlefield Rd
(415) 964-5111
Mountain View, CA 94043
MIL-SPEC and EIA/JESD (JEDEC) specifications
(Available from Global Engineering Documents)
800-854-7179 or
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.
8 Power Supply and Power Sequencing
This section provides design considerations for the MPC875/870 power supply. The MPC875/870 has a
core voltage (V
) and PLL voltage (V
), which both operate at a lower voltage than the I/O voltage
DDL
DDSYN
V
. The I/O section of the MPC875/870 is supplied with 3.3 V across V
and V (GND).
DDH
DDH SS
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 V
. In addition, 5 V-tolerant pins cannot exceed 5.5 V, and remaining input pins cannot
DDH
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:
•
•
V
V
must not exceed V
during power up and power down.
DDL
DDL
DDH
must not exceed 1.9 V, and V
must not exceed 3.465 V.
DDH
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.
MPC875/MPC870 Hardware Specifications, Rev. 3.0
Freescale Semiconductor
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
13
FREESCALE [ Freescale ]
