ATMEGA644PV ATMEL [ATMEL Corporation], ATMEGA644PV Datasheet - Page 239

• Manufacturer Part Number: ATMEGA644PV
• Description: 8-bit Microcontroller with 16/32/64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Figure 21-1. Analog-to-digital Converter Block Schematic
21.3
8011D–AVR–02/07
BANDGAP (1.1V)
ADC[7:0]
REFERENCE
REFERENCE
(1.1V/2.56V)
INTERNAL
AVCC
AREF
Operation
GND
8-BIT DATABUS
ADC[2:0]
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
the AREF pin minus 1 LSB. Optionally, AVCC or an internal 2.56V 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 and differential gain are 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. A selection of ADC input pins can be selected as
positive and negative inputs to the differential gain amplifier.
ADC MULTIPLEXER
SELECT (ADMUX)
INPUT
INPUT
NEG
MUX
POS
MUX
MUX DECODER
+
-
REGISTER B (ADCSRB)
ADC CTRL & STATUS
AMPLIFIER
GAIN
10-bit DAC
REGISTER A (ADCSRA)
ADC CTRL & STATUS
ADC CONVERSION
COMPLETE IRQ
PRESCALER
ATmega164P/324P/644P
CONVERSION LOGIC
+
-
ADTS[2:0]
START
TRIGGER
SELECT
SAMPLE & HOLD
INTERRUPT
COMPARATOR
ADC
MULTIPLEXER
OUTPUT
FLAGS
15
ADC DATA REGISTER
(ADCH/ADCL)
0
239