Datasheet

48
[Not recommended for new designs - Use XMEGA A1U series] XMEGA A1 [DATASHEET]
8067O–AVR–06/2013
26. ADC - 12-bit Analog to Digital Converter
26.1 Features
 Two ADCs with 12-bit resolution
 2Msps 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
26.2 Overview
XMEGA A1 devices have two Analog to Digital Converters (ADC), see Figure 26-1 on page 49. 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 capable 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.