39.2.1 Rev. A

– Wrong device ID when using debugWire

– Power consumption in power save modes

– USART start-up functionality not working

– External capacitor on AREF pin

– Increased power consumption when using voltage reference other than AVCC

1.) Wrong device ID when using debugWire

The device ID returned using debugWire is incorrect.

Problem Fix/Workaround

None.

2.) Power consumption in power save modes

Power consumption in power save modes will be higher due to improper control of internal power management.

Problem Fix/Workaround

None.

3.) USART start-up functionality not working

While in power save modes, the USART start bit detection logic fails to wake up the device.

Problem Fix/Workaround

None.

4.) External capacitor on AREF pin

If an external capacitor is used on the analog reference pin (AREF), it should be equal to or larger than 100nF. Smaller capacitor value can make the AREF buffer unstable with large ringing which will reduce the accuracy of the ADC.

Problem Fix/Workaround

None.

5. ) Increased power consumption when using voltage reference other than AVCC

Power consumption is higher when using internal or external voltage reference that is not equal to AVCC. The increased current consumption will be the same for active and all sleep modes, but the largest impact will be in low power sleep modes.

Problem Fix/Workaround

Select AVCC as ADC voltage reference before entering sleep mode to avoid extra power consumption during sleep. If no internal or external reference to the ADC is used, an external pull-down resistor should be added to the AREF pin.