Cautions - Intel PXA27 Series Design Manual

Mixed Voltage Design Considerations
4.4

Cautions

Observe the following cautions for proper operation and reliability of the PXA27x processor:
•
All power domains are equal to or lower than VCC_IO (excluding VCC_USB).
•
The application of VCC_BATT to the PXA27x processor from a state where there was no
voltage applied to VCC_BATT is referred to as start-of-date. If only VCC_BATT is applied at
the start-of-date, the current internal state of the PXA27x processor causes the current draw to
be higher than when the PXA27x processor is in deep sleep mode. Such a situation is
undesirable for systems that are production units, therefore, do not use these units
immediately. After the backup battery is initially installed, if the devices are not brought into at
least deep sleep mode through software, the backup battery experiences drainage. To avoid
drainage of backup battery and to allow the backup battery to remain connected after
production, boot the device and then place the device in deep sleep mode.
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Intel PXA27x Processor Family Design Guide