ATmega16 datasheet(205/357 Pages) ATMEL

205 / 357 page

205

2466S–AVR–05/09

ATmega16(L)

Figure 98. Analog to Digital Converter Block Schematic

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

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.

If differential channels are selected, the differential gain stage amplifies the voltage difference

between the selected input channel pair by the selected gain factor. This amplified value then

ADC CONVERSION

COMPLETE IRQ

8-BIT DATA BUS

ADC MULTIPLEXER

SELECT (ADMUX)

ADC CTRL. & STATUS

ADC DATA REGISTER

(ADCH/ADCL)

CONVERSION LOGIC

10-BIT DAC

SAMPLE & HOLD

COMPARATOR

INTERNAL 2.56V

REFERENCE

MUX DECODER

AVCC

ADC7

ADC6

ADC5

ADC4

ADC3

ADC2

ADC1

ADC0

ADC MULTIPLEXER

OUTPUT

GAIN

AMPLIFIER

AREF

BANDGAP

REFERENCE

PRESCALER

SINGLE ENDED / DIFFERENTIAL SELECTION

GND

POS.

INPUT

MUX

NEG.

INPUT

MUX

TRIGGER

SELECT

ADTS[2:0]

INTERRUPT

FLAGS

START

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