5-V Rail; 5-V Standby Rail; Vddh Rail; Vddl Bus - Freescale Semiconductor MPC8272ADS User Manual

Table 7-2. Maximum Power Consumption Per Add-In Card (continued)
7.1.1

5-V Rail

Some of the MPC8272ADS peripherals (not including the PCI add-in cards that should be
3.3 V only on the PCI interface, but can use 5 V for other components on-board) reside on
the 5-V bus. Because the MPC8272 is not 5-V tolerant, buffering is provided between 5V
peripherals and the MPC8272, protecting the MPC8272 from the higher voltage level.
7.1.2 3.3-V Rail
The MPC8272, SDRAM, PCI add-in cards, address and data buffers are powered by the 3.3
bus, which is produced from the ATX power supply.
7.1.3

5-V Standby Rail

The 5V standby power rail comes from the ATX Power Supply. Its only use is to power the
logic required to support the power button in the front panel on the ATX chassis.
7.1.4 V Rail
DDH
The MPC8272 V
DDH
drop linear voltage regulator MIC29501-3.3BU, made by Micrel.
A production option is made so that the level on this bus may be varied by means of
trimming the potentiometer TR2. Although this option requires replacing some
components, it allows the V
7.1.4.1 V Bus
DDL
The MPC8272 internal logic and the PLL are powered with a lower-voltage power source,
whose voltage may be in the range of 1.3V–1.7V.
A trimming potentiometer does the fine tuning within a range.
Changing the voltage to the core logic of the MPC8272 obviously has an influence over the
maximal speed of the core. The power-speed trade-off is that lower operation speeds may
be obtained with lower voltage supply.
Power Rail
-12V
power bus (3.3 V) is produced from the 5-V bus using a low-voltage
to be in the range of 3.0 V–3.6 V.
DDH
Chapter 7. Physical Properties
Add-In Card
100mA
Power Supply