Author: Rupali Honrao, Microchip Technology Inc.

This application note will explain how and when to use the powerful noise suppression features available on the Microchip tinyAVR® 0- and 1-series, and megaAVR® 0-series ADCs. In these ADCs, the input signal is fed through a Sample-and-Hold circuit which ensures that the input voltage to the ADC is held at a constant level during sampling.

The ADC supports sampling in bursts where a configurable number of conversion results are accumulated into a single ADC result (sample accumulation). Further, a sample delay can be configured to tune the ADC sampling frequency associated with a single burst. This is done to tune the sampling frequency away from any harmonic noise aliased with the ADC sampling frequency (within the burst) from the sampled signal. An automatic sampling delay variation feature can be used to randomize this delay to slightly change the time between samples.

In this case, a test and verification setup is suggested. The topics covered include using the ADC hardware sample accumulator to filter out zero mean random noise, and surpassing harmonic noise through tuned sampling delays or automatic sampling delay variation. A test setup for generating noisy signals is suggested and directions on how to illustrate the results in the Atmel Studio Data Visualizer are provided.

The example code for replicating the results described in this application note is available from Atmel | START:

Additional details on ADC performance and general configuration are available in the device data sheet.