ATMEga64L ATMEL Corporation, ATMEga64L Datasheet - Page 231

• Manufacturer Part Number: ATMEga64L
• Description: 8-bit AVR Microcontroller with 64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

Operation
2490G–AVR–03/04
Figure 108. Analog to Digital Converter Block Schematic
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, AVCC or an internal 2.56V refer-
ence 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 refer-
ence, 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 dif-
ference between the selected input channel pair by the selected gain factor. This
amplified value then becomes the analog input to the ADC. If single ended channels are
used, the gain amplifier is bypassed altogether.
AREF
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
AVCC
GND
INTERNAL 2.56V
REFERENCE
REFERENCE
8-BIT DATA BUS
BANDGAP
INPUT
INPUT
POS.
NEG.
MUX
MUX
ADC MULTIPLEXER
SELECT (ADMUX)
MUX DECODER
+
-
SINGLE ENDED / DIFFERENTIAL SELECTION
GAIN
AMPLIFIER
10-BIT DAC
ADC CTRL. & STATUS
REGISTER (ADCSRA)
ADC CONVERSION
COMPLETE IRQ
PRESCALER
CONVERSION LOGIC
ADTS[2:0]
ATmega64(L)
INTERRUPT
TRIGGER
SELECT
FLAGS
SAMPLE & HOLD
COMPARATOR
15
+
-
ADC DATA REGISTER
(ADCH/ADCL)
ADC MULTIPLEXER
OUTPUT
0
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