We can proceed AVR MCU ATXMEGA256A3 Heximal Extraction, please view the AVR MCU ATXMEGA256A3 features for your reference:

Maximum operating frequency below 1.76V is 8 MHz
To ensure correct operation, the maximum operating frequency below 1.76V VCC is 8 MHz.
Problem fix/Workaround
None, avoid running the device outside this frequency and voltage limitation.

Bandgap voltage input for the ACs cannot be changed when used for both ACs simultaneously ADC gain stage output range is limited to 2.4V Sampled BOD in Active mode will cause noise when bandgap is used as reference

Flash Power Reduction Mode can not be enabled when entering sleep mode JTAG enable does not override

Analog Comparator B output Bandgap measurement with the ADC is non-functional when VCC is below 2.7V

DAC refresh may be blocked in S/H mode

BOD will be enabled after any reset

Both DFLLs and both oscillators has to be enabled for one to work

Operating frequnecy and voltage limitations

Bandgap voltage input for the ACs cannot be changed when used for both ACs simultaneously

If the bandgap voltage is selected as input for one Analog Comparator (AC) and then selected/deselected as input for the another AC, the first comparator will be affected for up to 1 us and could potentially give a wrong comparison result.

Problem fix/Workaround

If the Bandgap is required for both ACs simultaneously, configure the input selection for both ACs before enabling any of them before AVR MCU ATXMEGA256A3 Heximal Extraction.

ADC gain stage output range is limited to 2.4 V

The amplified output of the ADC gain stage will never go above 2.4 V, hence the differential input will only give correct output when below 2.4 V/gain. For the available gain settings, this gives a differential input range of voltages;