398
8331B–AVR–03/12
Atmel AVR XMEGA AU
30. AC – Analog Comparator
30.1
Features
•
Selectable propagation delay versus current consumption
•
Selectable hysteresis
– None
– 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 V
CC
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
30.2
Overview
The analog comparator (AC) compares the voltage levels on two inputs and gives a digital out-
put based on this comparison. The analog comparator may be configured to generate interrupt
requests and/or events upon several different combinations of input change.
Two important properties of the analog comparator’s dynamic behavior are: hysteresis and prop-
agation delay. Both of these parameters may be adjusted in order to achieve the optimal
operation for each application.
The input selection includes analog port pins, several internal signals, and a 64-level program-
mable voltage scaler. The analog comparator output state can also be output on a pin for use by
external devices.
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. These are called analog
comparator 0 (AC0) and analog comparator 1 (AC1). They have identical behavior, but separate
control registers. Used as pair, they can be set in window mode to compare a signal to a voltage
range instead of a voltage level.
