Datasheet

123
2586N–AVR–04/11
ATtiny25/45/85
16. Analog Comparator
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 can trigger a separate inter-
rupt, 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 Figure 16-1.
Figure 16-1. Analog Comparator Block Diagram
Notes: 1. See Table 16-1 below.
See Figure 1-1 on page 2 and Table 10-5 on page 65 for Analog Comparator pin placement.
16.1 Analog Comparator Multiplexed Input
When the Analog to Digital Converter (ADC) is configurated as single ended input channel, it is
possible to select any of the ADC[3:0] pins to replace the negative input to the Analog Compara-
tor. 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
ADCSRB) is set and the ADC is switched off (ADEN in ADCSRA is zero), MUX[1:0] in ADMUX
select the input pin to replace the negative input to the Analog Comparator, as shown in Table
16-1. If ACME is cleared or ADEN is set, AIN1 is applied to the negative input to the Analog
Comparator.
ACD
+
_
VCC
ACBG
ACI
ACO
ACIE
ACIS1 ACIS0
IN T ERRU P T
SEL ECT
ANALOG
COMPA RATO
R
IRQ
AIN0
AIN1
INTERNAL 1.1V
REF EREN C E
ADC MULTIPLEXER
OUTPUT
ACME
ADEN
(1)
Table 16-1. Analog Comparator Multiplexed Input
ACME ADEN MUX[1:0] Analog Comparator Negative Input
0x xxAIN1
11 xxAIN1
10 00ADC0
10 01ADC1
10 10ADC2
10 11ADC3