Datasheet

207
ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
Figure 21-1. Analog to Digital Converter Block Schematic Operation
The ADC converts an analog input voltage to a 10-bit digital value through successive approximation. The minimum value
represents GND and the maximum value represents the voltage on the AREF pin minus 1 LSB. Optionally, AV
CC
or an
internal 1.1V reference voltage may be connected to the AREF pin by writing to the REFSn bits in the ADMUX register. The
internal voltage reference may thus be decoupled by an external capacitor at the AREF pin to improve noise immunity.
The analog input channel is selected by writing to the MUX bits in ADMUX. Any of the ADC input pins, as well as GND and a
fixed bandgap voltage reference, can be selected as single ended inputs to the ADC. The ADC is enabled by setting the
ADC enable bit, ADEN in ADCSRA. Voltage reference and input channel selections will not go into effect until ADEN is set.
The ADC does not consume power when ADEN is cleared, so it is recommended to switch off the ADC before entering
power saving sleep modes.
Prescaler
-
+
15 0
ADC Multiplexer
Select (ADMUX)
MUX Decoder
AVCC
8-Bit Data Bus
AREF
AREF
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
10-Bit DAC
Input
MUX
Sample and Hold
Comparator
Internal 1.1V
Reference
Conversion Logic
ADC Conversion
Complete IRQ
ADC CTRL and Status
Register (ADCSRA)
ADC Data Register
(ADCH/ADCL)
ADIF
ADEN
REFS1 REFS0
ADLAR
MUX3 MUX2 MUX1 MUX0
Channel Selection
ADSC
ADIF
ADFR
ADPS2 ADPS1 ADPS0
ADIE
Bandgap
Reference
ADC[9:0]
ADC
Multiplexer
Output