Datasheet

142
8197C–AVR–05/11
ATtiny261A/461A/861A
Figure 15-1. Analog to Digital Converter Block Schematic
15.3 Operation
The ADC converts an analog input voltage to a 10-bit digital value through successive approxi-
mation. The minimum value represents GND and the maximum value represents the voltage on
V
CC
, the voltage on the AREF pin or an internal 1.1V / 2.56V voltage reference.
The voltage reference for the ADC may be selected by writing to the REFS[2:0] bits in ADCSRB
and ADMUX registers. The VCC supply, the AREF pin or an internal 1.1V / 2.56V voltage refer-
ence may be selected as the ADC voltage reference. Optionally the internal 1.1V / 2.56V voltage
ADC CONVERSION
COMPLETE IRQ
8-BIT DATA BUS
15 0
ADC MULTIPLEXER
SELECT (ADMUX)
ADC CTRL. & STATUS
REGISTER A (ADCSRA)
ADC DATA REGISTER
(ADCH/ADCL)
MUX2
ADIE
ADATE
ADSC
ADEN
ADIF
ADIF
MUX1
MUX0
ADPS0
ADPS1
ADPS2
MUX3
CONVERSION LOGIC
10-BIT DAC
+
-
SAMPLE & HOLD
COMPARATOR
MUX DECODER
MUX4
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
REFS0
REFS1
ADLAR
+
-
CHANNEL SELECTION
GAIN SELECTION
ADC[9:0]
ADC
MULTIPLEXER OUTPUT
GAIN
AMPLIFIER
INTERNAL 1.1V
REFERENCE
PRESCALER
SINGLE ENDED /
DIFFERENTIAL SELECTION
AGND
POS.
INPUT
MUX
NEG.
INPUT
MUX
ADC10
ADC9
ADC8
VCC
AREF
TEMPERATURE
SENSOR
INTERNAL 2.56/1.1V
REFERENCE
MUX
ADC CTRL. & STATUS
REGISTER B (ADCSRB)
REFS2
GSEL
MUX5