Personal Computer User Manual

Intel® PXA27x Processor Family Power Requirements
10 Application Note
2.1.2 Power Supply Configuration in a Minimal System
For minimal systems, only five (four if VCC_USIM is disabled) regulators are required to power
the PXA27x processor and its input/output interfaces, as shown in Table 3.
VCC_IO Fixed 3.0 V or 3.3 V (±10%) for standard CMOS I/Os interfacing to external
components, which are also supplied from fixed 3.0 V or 3.3 V. The I/Os for external
components connected to the corresponding signals on the PXA27x processor must be
supplied from the same regulator. Driving VCC_BATT in this manner prevents forward-
biasing of protection diodes and inadvertent charging of the backup battery through
inputs on the PXA27x processor VCC_REG domain. The VCC_IO supply must be the
highest potential in the system (excluding VCC_BATT and VCC_USB) and must be
sequenced on at the same time or before the other supplies enabled by SYS_EN.
VCC_IO are connected to any of the VCC_LCD, VCC_MEM, VCC_BB or VCC_USIM
supplies as long as none of these supplies are driven at a voltage higher than VCC_IO.
VCC_IO must be enabled when SYS_EN is asserted and disabled when SYS_EN is
de-asserted.
NOTE: When the main battery is installed, VCC_BATT must be driven by a regulator
whose output is matched to the VCC_IO regulator so that VCC_IO and
VCC_BATT remain within 200 mV of each other when the VCC_IO regulator is
enabled.
VCC_LCD Power for output drivers to LCD panel, 1.8 V (+20%, -5%), 2.5 V, 3.0V or 3.3 V (± 10%).
Optionally, these are strapped to one of the existing I/O supplies at 3.3 V, 2.5 V, or
1.8 V if appropriate for the panel used. This supply must be enabled when SYS_EN is
asserted and disabled when SYS_EN is de-asserted.
VCC_MEM Power for memory/system bus I/O at 1.8 V (+20%, -5%), 2.5 V, 3.0V or 3.3 V (±10%);
fixed, strappable by input signals on the power controller to one of these voltages. The
power controller automatically powers up VCC_MEM to the voltage specified by its
input control signals when this regulator is enabled. Corresponding I/Os of the memory
components or companion chips must be powered from the same regulator. This
supply must be enabled when SYS_EN is asserted and disabled when SYS_EN is
de-asserted.
VCC_BB Power for I/Os to an external baseband module or device, at 1.8 V (+20%, -5%), 2.5 V,
3.0V,or 3.3 V (±10%). Corresponding I/Os of the baseband device must be powered
from the same regulator. In systems that use PCMCIA or Compact flash and the
baseband interface, VCC_BB must be tied to VCC_MEM because some of the card
interface signals are multiplexed with baseband interface signals. This supply must be
enabled when SYS_EN is asserted and disabled when SYS_EN is de-asserted if any of
these GPIOs are used (as either a GPIO or as an alternate function): GPIO<48>,
GPIO<57:50>, GPIO<85:81>.
VCC_USIM Power for I/Os to an external Universal Subscriber Identity Module (USIM) card. The
VCC_USIM voltage generated by the PMIC is software configurable at settings of 1.8 V
(+20%, -5%) or 3.0 V (± 10%) or disabled (0 V). The software voltage control is
implemented using I
2
C commands or the PMIC decodes the PXA27x processor UVS0,
nUVS1, and nUVS2 outputs. Refer to Section 4.7, “Universal Subscriber Identity
Module (USIM)” on page 21 for more information.
VCC_USB Power for USB at 3.0 V or 3.3V (±10%) for standard differential USB I/Os interfacing to
external components, which are also supplied from fixed 3.0 V or 3.3 V.
NOTE: VCC_USB powers the I/O for the USB interfaces, the USB differential signals
D+. D- is out of compliance with the USB specification if VCC_USB is below
2.8 V.
NOTE: The +5 V VBUS source from USB host controller, which must be available for
bus-powered peripherals, must be supplied from an external source, but it is
not part of the PXA27x processor silicon.
Table 2. Intel® PXA27x Processor Voltage Domains (Sheet 2 of 2)
Voltage Description