The Atmel® | SMART SAM V/E/S7x series are high-performance, power-efficient embedded MCUs based on the ARM® Cortex®-M7 processor. Analog-to-digital converters translate analog measurements, characteristic of most phenomena in the real world, to digital format, used in information processing, computing, data transmission, and control systems. The purpose of this application note is to propose a method of offset and gain calibration using digital processing including the average and the calibration registers. An efficient way to generate the analog levels used in the calibration is also proposed.
The AFE implements a cyclic ADC architecture. After an input sampling, the ADC processes the voltage in 12 steps, using 23 AFE clock cycles. As illustrated in the above figure, the AFE is built as a differential AFE. This capability provides a good common mode noise rejection which is essential in a microcontroller working at high clock frequency. Without this differential design, the ADC aliases the noise of the microcontroller digital activity and drastically reduces performance.