ATmega88 datasheet(238/340 Pages) ATMEL

238 / 340 page

238

7530H–AVR–02/09

ATmega48/88/168 Automotive

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 approxi-

mation. 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 con-

nected 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. Volt-

age 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.

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 1.1V

REFERENCE

MUX DECODER

AVCC

ADC7

ADC6

ADC5

ADC4

ADC3

ADC2

ADC1

ADC0

ADC MULTIPLEXER

OUTPUT

AREF

BANDGAP

REFERENCE

PRESCALER

GND

INPUT

MUX

ATmega88 Datasheet(PDF) 238 Page - ATMEL Corporation

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