10 adc accuracy definitions – Rainbow Electronics ATtiny43U User Manual
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• Keep analog tracks well away from high-speed switching digital tracks.
• Use the ADC noise canceler function to reduce induced noise from the CPU.
• If any port pin is used as a digital output, it mustn’t switch while a conversion is in progress.
• Place bypass capacitors as close to V
CC
and GND pins as possible.
Where high ADC accuracy is required it is recommended to use ADC Noise Reduction Mode, as
described in
. This is especially the case when system clock frequency
is above 1 MHz, or when the ADC is used for reading the internal temperature sensor. A good
system design with properly placed, external bypass capacitors does reduce the need for using
ADC Noise Reduction Mode
16.10 ADC Accuracy Definitions
An n-bit single-ended ADC converts a voltage linearly between GND and V
REF
in 2
n
steps
(LSBs). The lowest code is read as 0, and the highest code is read as 2
n
-1.
Several parameters describe the deviation from the ideal behavior:
• Offset: The deviation of the first transition (0x000 to 0x001) compared to the ideal transition
(at 0.5 LSB). Ideal value: 0 LSB.
Figure 16-9. Offset Error
Output Code
V
REF
Input Voltage
Ideal ADC
Actual ADC
Offset
Error