ATXMEGA256A3_10 Datasheet, PDF (98/110 Pages) ATMEL Corporation – 8/16-bit AVR XMEGA A3 Microcontroller

XMEGA A3
11. Inverted I/O enable does not affect Analog Comparator Output
The inverted I/O pin function does not affect the Analog Comparator output function.
Problem fix/Workarund
Configure the analog comparator setup to give a inverted result (i.e. connect positive input to
the negative AC input and vice versa), or use and externel inverter to change polarity of
Analog Comparator Output.
36.2 ATxmega192A3, ATxmega128A3, ATxmega64A3
36.2.1 rev. B
• 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
• Bandgap measurement with the ADC is non-functional when V_CC is below 2.7V
• BOD will be enabled after any reset
• Writing EEPROM or Flash while reading any of them 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
• Inverted I/O enable does not affect Analog Comparator Output
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 them.
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, this
gives a differential input range of:
– 1x gain:
– 2x gain:
– 4x gain:
– 8x gain:
– 16x gain:
– 32x gain:
– 64x gain:
2.4 V
1.2 V
0.6 V
300 mV
150 mV
75 mV
38 mV
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8068R–AVR–08/10