During periods of low VDD, the Flash program or EEPROM data can be
corrupted if the supply voltage is too low for the CPU and the Flash/EEPROM to operate
properly. These issues are the same as for board level systems using Flash/EEPROM, and the
same design solutions should be applied.
A Flash/EEPROM corruption can be caused by two situations
when the voltage is too low:
- 1.A regular write sequence to the Flash, which requires a minimum
voltage to operate correctly.
- 2.The CPU itself can execute instructions incorrectly when the
supply voltage is too low.
See the Electrical Characteristics chapter for Maximum Frequency
vs. V
DD.
Flash/EEPROM corruption can be avoided by these measures:
- Keep the device in Reset during periods of insufficient power
supply voltage. This can be done by enabling the internal Brown-Out
Detector (BOD).
- The voltage level monitor in the BOD can be used to prevent
starting a write to the EEPROM close to the BOD level.
- If the detection levels of the internal BOD don’t match the
required detection level, an external low VDD Reset
protection circuit can be used. If a Reset occurs while a write
operation is ongoing, the write operation will be aborted.