PowerQUICC III MPC8555E and MPC8541E Bring-Up Guidelines, Rev. 5
4
Freescale Semiconductor
Power
III are 5-V-tolerant. All input signals need to meet the G/L/OV
IN
DC specification of the respective I/O
block.
2.2
Power Consumption
The MPC8555EEC and the MPC8541EEC hardware specifications provide estimated power dissipation
for various frequency configurations of the core complex bus (CCB) clock and the e500 core frequencies.
Suitable thermal management is required to ensure that the junction temperature does not exceed the
maximum specified value. The numbers provided in the hardware specification include dissipation for all
blocks except the PLL supplies and the I/Os. Both must be added to the typical number to determine
accurately whether a heat sink or other form of chip cooling mechanism is required.
2.3
Power Sequencing
One consequence of multiple power supplies is that when power is initially applied, the voltage rails ramp
up at different rates. These rates depend on the power supply, the type of load on each power supply, and
the way different voltages are derived. The MPC8555E and MPC8541E require the power rails to be
applied in a specific sequence to ensure proper device operation. The requirements for power-up are as
follows:
1. V
DD
, AV
DD
2. GV
DD
, LV
DD
, OV
DD
(I/O supplies)
Items on the same line have no ordering requirements with respect to one another. Items on separate lines
must be ordered sequentially so that voltage rails on a previous step reach 90 percent of their value before
the voltage rails on the current step reach 10 percent of theirs. If the items on line 2 must precede items on
line 1, take care to ensure that the delay does not exceed 50 mS and that the power sequence is not
performed more than once per day in a production environment.
NOTE
To guarantee MCKE low during power-up, GVDD should be the last power
supply to come up. If there is no concern about any of the DDR signals being
in an indeterminate state during power-up, then the sequencing is not
required.
Table 1. Power Supplies
Type
Name
Block
(V)
Core
V
DD
—
1.2
PLL
AV
DD
Core PLL, Platform PLL, CPM PLL, PCI1, PCI2
1.2
I/O
GV
DD
DDR
2.5
I/O
LV
DD
TSEC
2.5 / 3.3
I/O
OV
DD
CPM, LBIU, DMA, MII-mgt, PIC1, PCI2,
I
2
C
3.3
