Datasheet

8116J–AVR–06/2013

XMEGA A3B

Not recommended for new designs -

Use ATxmega256A3BU

25. ADC - 12-bit Analog to Digital Converter

25.1 Features

• Two ADCs with 12-bit resolution

• 2 Msps sample rate for each ADC

• Signed and Unsigned conversions

• 4 result registers with individual input channel control for each ADC

• 8 single ended inputs for each ADC

• 8x4 differential inputs for each ADC

• 4 internal inputs:

– Integrated Temperature Sensor

– DAC Output

– VCC voltage divided by 10

– Bandgap voltage

• Software selectable gain of 2, 4, 8, 16, 32 or 64

• Software selectable resolution of 8- or 12-bit.

• Internal or External Reference selection

• Event triggered conversion for accurate timing

• DMA transfer of conversion results

• Interrupt/Event on compare result

25.2 Overview

XMEGA A3B devices have two Analog to Digital Converters (ADC), see Figure 25-1 on page 43.

The two ADC modules can be operated simultaneously, individually or synchronized.

The ADC converts analog voltages to digital values. The ADC has 12-bit resolution and is capa-

ble of converting up to 2 million samples per second. The input selection is flexible, and both

single-ended and differential measurements can be done. For differential measurements an

optional gain stage is available to increase the dynamic range. In addition several internal signal

inputs are available. The ADC can provide both signed and unsigned results.

This is a pipeline ADC. A pipeline ADC consists of several consecutive stages, where each

stage convert one part of the result. The pipeline design enables high sample rate at low clock

speeds, and remove limitations on samples speed versus propagation delay. This also means

that a new analog voltage can be sampled and a new ADC measurement started while other

ADC measurements are ongoing.

ADC measurements can either be started by application software or an incoming event from

another peripheral in the device. Four different result registers with individual input selection

(MUX selection) are provided to make it easier for the application to keep track of the data. Each

result register and MUX selection pair is referred to as an ADC Channel. It is possible to use

DMA to move ADC results directly to memory or peripherals when conversions are done.

Both internal and external analog reference voltages can be used. An accurate internal 1.0V

reference is available.

An integrated temperature sensor is available and the output from this can be measured with the

ADC. The output from the DAC, VCC/10 and the Bandgap voltage can also be measured by the

ADC.