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 Locked AVR ATXMEGA128A3 Code Reading has been carried on:
Bandgap measurement with the ADC is non-functional when VCC is below 2.7V
BOD will be enabled after any reset
Writing EEPROM or Flash while reading MCU will not work
ADC has increased INL error for some operating conditions
DAC has increased INL or noise for some operating conditions
VCC voltage scaler for AC is non-linear
Maximum operating frequency below 1.76V is 8 MHz
1. 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 Microcontroller Unlocking.
2. 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;
Problem fix/Workaround
Keep the amplified voltage output from the ADC gain stage below 2.4 V in order to get a correct result, or keep ADC voltage reference below 2.4 V.
Sampled BOD in Active mode will cause noise when bandgap is used as reference
Using the BOD in sampled mode when the device is running in Active or Idle mode will add noise on the bandgap reference for ADC, DAC and Analog Comparator.
Problem fix/Workaround
If the bandgap is used for Locked AVR ATXMEGA128A3 Code Reading, then either the ADC, DAC and Analog Comparator, the BOD must not be set in sampled mode.
Bandgap measurement with the ADC is non-functional when VCC is below 2.7V
The ADC cannot be used to do bandgap measurements when VCC is below 2.7V.
Problem fix/Workaround
If internal voltages must be measured when VCC is below 2.7V, measure the internal 1.00V reference instead of the bandgap.
BOD will be enabled after any reset
If any reset source goes active, the BOD will be enabled and keep the device in reset if the VCC voltage is below the programmed BOD level. During Power-On Reset, reset will not be released until VCC is above the programmed BOD level even if the BOD is disabled.
Problem fix/Workaround
Do not set the BOD level higher than VCC even if the BOD is not used.
