Phytec phyCORE-OMAP44 Series, Руководство по оборудованию

Страница: 52 / 168

Part I: PCM-049/phyCORE-OMAP44xx System on Module phyCORE-OMAP44xx
40 ©
PHYTEC Messtechnik GmbH
2012
L-760e_1
1.4.4 Reference Voltages
The voltage level of the phyCOREs logic circuitry is VCC_1V8_IO (1.8 V) which is generated on-board. In order to
allow connecting external devices to the phyCORE-OMAP44xx without the need of another voltage source in
addition to the primary supply this voltage is brought out at pin X1B30 of the phyCORE-Connector.
Use of level shifters supplied with VCC_1V8_IO allows converting the signals according to the needs on the
custom target hardware. Alternatively signals can be connected to an open drain circuitry with a pull-up resistor
attached to VCC_1V8_IO.
Further reference voltages are VCC_MMC1 and VCC_3V3_S:
VCC_MMC1 is needed because the MMC1 supply voltage can be switched between 1.8 V and the default 3 V by
setting the corresponding register of the PMIC. The MMC1 reference voltage is brought out at pin X1B18.
VCC_3V3_S is the reference voltage of the switchable 3.3 V domain which provides the supply the voltages of
the RS-232 transceiver, the Ethernet controller and the USB PHY. This reference voltage can be used e.g. to
switching the center tap supply voltage of the Ethernet transformer to avoid non wanted back current to the
module if 3V3_S is turned off during standby. The VCC_3V3_S reference voltage is brought out at pin X1D23.
Please take care not to load the reference voltage too heavily to avoid any disfunction or damage of the module.
The following maximum loads are allowed:
• VCC_1V8_IO (1.8 V): 400 mA
• VCC_MMC1 (3 V/1.8 V): 150 mA
• VCC_3V3_S (3.3 V): 500 mA