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P5040/P5020 Reference Design Board User Guide, Rev. 0
38
Freescale Semiconductor
Architecture
5.3.1.10
USB
USB voltages has the following characteristics:
•
USB transceiver: USB_VDD_3P3 voltage is set to 3.3V.
•
USB PLL: USB_VDD_1P0 voltage is set to 1.0V.
•
External periphery device power: USB1_VBUS, USB2_VBUS voltage = 5V corresponds to
USB1_PWR_EN, USB2_PWR_EN signal; otherwise, [default] USB_VBUS = 0V.
5.3.1.11
VDD_LP
VDD_LP voltage has the following characteristics:
•
VDD_LP = 1.0V.
•
Low-power security monitor supply: VCC_HOT3V3 or onboard battery BT1 (which is
independent of the main PS) supply voltage to the VDD_LP via LDO regulator U21.
•
When the main ATX PS is powered and connected to the RDB (VCC_HOT3V3 is present) then
voltage is supplied to the CPU. Alternatively, the battery can supply voltage if J9 is “shorted.”
•
Auxiliary J10, VDD_LP_DET, provides low-power, tamper detect functionality.
This table lists all possible VDD_LP voltage options.
5.4
Clocks
The reference board clock signals are generated by the board in use.
lists the requirements of the
reference board clock signals when the reference board is populated with a P5040 or P5020 processor. This
board uses a custom IDT 6T49278BNLGI8 clock to meet the requirements listed in the table below.
Table 18. VDD_LP Voltage Options
VDD_LP
J10
J9
VCC_HOT3V3
Battery
VDD_LP_TMP_DETECT
1.0V
1-2
2-3
X
Existing
X
On
Off
1-2
2-3
Short
X
Existing
On
Off
0V
X
X
Not existing
Not existing
X