attiny13-20ss ATMEL Corporation, attiny13-20ss Datasheet - Page 89

• Manufacturer Part Number: attiny13-20ss
• Description: 8-bit Microcontroller With 1k Bytes In-system Programmable Flash - Atmel Corporation
• Manufacturer: ATMEL Corporation

Analog Noise Canceling
Techniques
ADC Accuracy Definitions
2535G–AVR–01/07
Digital circuitry inside and outside the device generates EMI which might affect the
accuracy of analog measurements. If conversion accuracy is critical, the noise level can
be reduced by applying the following techniques:
An n-bit single-ended ADC converts a voltage linearly between GND and V
steps (LSBs). The lowest code is read as 0, and the highest code is read as 2
Several parameters describe the deviation from the ideal behavior:
•
Figure 48. Offset Error
•
1. Keep analog signal paths as short as possible. Make sure analog tracks run
2. Use the ADC noise canceler function to reduce induced noise from the CPU.
3. If any port pins are used as digital outputs, it is essential that these do not
Offset: The deviation of the first transition (0x000 to 0x001) compared to the ideal
transition (at 0.5 LSB). Ideal value: 0 LSB.
Gain Error: After adjusting for offset, the Gain Error is found as the deviation of the
last transition (0x3FE to 0x3FF) compared to the ideal transition (at 1.5 LSB below
maximum). Ideal value: 0 LSB
over the analog ground plane, and keep them well away from high-speed
switching digital tracks.
switch while a conversion is in progress.
Output Code
Offset
Error
V
REF
Input Voltage
Ideal ADC
Actual ADC
n
-1.
REF
in 2
89
n