Datasheet

27. Analog Comparator
27.1. Overview
The Analog Comparator compares the input values on the positive pin AIN0 and negative pin AIN1. When
the voltage on the positive pin AIN0 is higher than the voltage on the negative pin AIN1, the Analog
Comparator Output, ACO, is set. The comparator’s output can be set to trigger the Timer/Counter1 Input
Capture function. In addition, the comparator can trigger a separate interrupt, exclusive to the Analog
Comparator. The user can select Interrupt triggering on comparator output rise, fall or toggle. A block
diagram of the comparator and its surrounding logic is shown in the figure below.
Figure 27-1 Analog Comparator Block Diagram
ACBG
BANDGAP
REFERENCE
ADC MULTIPLEXER
OUTPUT
ACME
ADEN
(1)
Note:
1. See table Analog Comparator Multiplexed Input in the section below.
2. Refer to figure Pinout ATmega64A in Pin Configurations and table Port E Pins Alternate Functions
in Alternate Functions of Port E for Analog Comparator pin placement.
Related Links
Pin Configurations on page 14
Alternate Functions of Port E on page 105
27.2. Analog Comparator Multiplexed Input
It is possible to select any of the ADC7:0 pins to replace the negative input to the Analog Comparator.
The ADC multiplexer is used to select this input, and consequently, the ADC must be switched off to
utilize this feature. If the Analog Comparator Multiplexer Enable bit (ACME in SFIOR) is set and the ADC
is switched off (ADEN in ADCSRA is zero), MUX2:0 in ADMUX select the input pin to replace the
negative input to the Analog Comparator, as shown in the following table. If ACME is cleared or ADEN is
set, AIN1 is applied to the negative input to the Analog Comparator.
Atmel ATmega64A [DATASHEET]
Atmel-8160E-ATmega64A_Datasheet_Complete-09/2015
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