Datasheet

307
XMEGA D4 [DATASHEET]
8135P–AVR–01/2014
1. Bandgap voltage input for the ACs can not 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 another AC, the first comparator will be affected for up to 1 ìs 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. VCC voltage scaler for AC is non-linear
The 6-bit VCC voltage scaler in the Analog Comparators is non-linear.
Figure 34-1. Analog Comparator Voltage Scaler vs. Scalefac
T = 25°C
Problem fix/Workaround
Use external voltage input for the analog comparator if accurate voltage levels are needed.
3. ADC has increased INL error for some operating conditions
Some ADC configurations or operating condition will result in increased INL error.
In signed mode INL is increased to:
 6LSB for sample rates above 130ksps, and up to 8LSB for 200ksps sample rate.
 6LSB for reference voltage below 1.1V when VCC is above 3.0V.
 20LSB for ambient temperature below 0 degree C and reference voltage below 1.3V.
In unsigned mode, the INL error cannot be guaranteed, and this mode should not be used.
Problem fix/Workaround
None. Avoid using the ADC in the above configurations in order to prevent increased INL error. Use the ADC in
signed mode also for single ended measurements.
5. ADC gain stage output range is limited to 2.4V
The amplified output of the ADC gain stage will never go above 2.4V, hence the differential input will only give cor-
rect output when below 2.4V/gain. For the available gain settings, this gives a differential input range of:
3.3V
2.7V
1.8V
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20 25 30 35 40 45 50 55 60 65
SCALEFAC
V
SCALE
[V]