ATXMEGA256A3U Datasheet, PDF (48/116 Pages) ATMEL Corporation – 8/16-bit Atmel XMEGA A3U Microcontroller

XMEGA A3U
29. AC - Analog Comparator
29.1 Features
29.2 Overview
• Four Analog Comparators
• Selectable propagation delay vs current consumption
• Selectable hysteresis
– No
– Small
– Large
• Analog Comparator output available on pin
• Flexible Input Selection
– All pins on the port
– Output from the DAC
– Bandgap reference voltage.
– A 64-level programmable voltage scaler of the internal VCC voltage
• Interrupt and event generation on
– Rising edge
– Falling edge
– Toggle
• Window function interrupt and event generation on
– Signal above window
– Signal inside window
– Signal below window
• Constant current source with configurable output pin selection
The Analog Comparator (AC) compares the voltage level on two inputs and gives a digital output
based on this comparison. The Analog Comparator may be configured to give interrupt requests
and/or events upon several different combinations of input change.
Two important properties of the Analog Comparator when it comes to the dynamic behavior, are
hysteresis and propagation delay. Both these parameters may be adjusted in order to find the
optimal operation for each application.
The input section includes analog port pins, several internal signals and a 64-level programma-
ble voltage scaler. The analog comparator output state can also be directly available on a pin for
use by external devices. Using as pair they can also be set in Window mode to monitor a signal
compared to a voltage window instead of a voltage level.
A constant current source can be enabled, and output on a selectable pin. This can be used to
replace for example external resistors used to charge capacitors in capacitive touch sensing
applications.
The Analog Comparators are always grouped in pairs on each port. They have identical behav-
ior but separate control registers.
PORTA and PORTB each has one AC pair. Notations are ACA and ACB, respectively.
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