atxmega192a1-au ATMEL Corporation, atxmega192a1-au Datasheet - Page 91

• Manufacturer Part Number: atxmega192a1-au
• Description: 8/16-bit Xmega A1 Microcontroller
• Manufacturer: ATMEL Corporation

8067M–AVR–09/10
1. Bandgap voltage input for the ACs cannot be changed when used for both ACs
2. VCC voltage scaler for AC is non-linear
Figure 35-1. Analog Comparator Voltage Scaler vs. Scalefac
3. The ADC has up to ±2 LSB inaccuracy
4. ADC gain stage output range is limited to 2.4 V
simultaneously
If the Bandgap voltage is selected as input for one Analog Comparator (AC) and then
selected/deselected as input for another AC, the first comparator will be affected for up to
1 µs 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.
The 6-bit VCC voltage scaler in the Analog Comparators is non-linear.
Problem fix/Workaround
Use external voltage input for the analog comparator if accurate voltage levels are needed
The ADC will have up to ±2 LSB inaccuracy, visible as a saw-tooth pattern on the input volt-
age/ output value transfer function of the ADC. The inaccuracy increases with increasing
voltage reference reaching ±2 LSB with 3V reference.
Problem fix/Workaround
None, the actual ADC resolution will be reduced with up to ±2 LSB.
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:
3.5
2.5
1.5
0.5
3
2
1
0
0
T = 25°C
5
10
15
20
25
SCALEFAC
30
35
40
45
50
55
XMEGA A1
60
65
3.3 V
2.7 V
1.8 V
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