ATA8742 ATMEL Corporation, ATA8742 Datasheet - Page 155

• Manufacturer Part Number: ATA8742
• Manufacturer: ATMEL Corporation

25.3
9151A–INDCO–07/09
ADC Operation
Figure 25-1. Analog to Digital Converter Block Schematic
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 reference
voltage.The voltage reference for the ADC may be selected by writing to the REFS1..0 bits in
ADMUX. The VCC supply, the AREF pin or an internal 1.1V voltage reference may be selected
as the ADC voltage reference.
The analog input channel and differential gain are selected by writing to the MUX5..0 bits in
ADMUX. Any of the eight ADC input pins ADC7..0 can be selected as single ended inputs to the
ADC. For differential measurements all analog inputs next to each other can be selected as a
input pair. Every input is also possible to measure with ADC3. These pairs of differential inputs
are measured by ADC trough the differential gain amplifier.
If differential channels are selected, the differential gain stage amplifies the voltage difference
between the selected input pair by the selected gain factor, 1x or 20x, according to the setting of
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
AREF
V
CC
TEMPERATURE
REFERENCE
INTERNAL
8-BIT DATA BUS
AGND
ADC CTRL. & STATUS B
SENSOR
REGISTER (ADCSRB)
1.1V
ADC8
INPUT
INPUT
POS.
NEG.
MUX
ADTS2...ADTS0
MUX
ADC MULTIPLEXER
MUX DECODER
SELECT (ADMUX)
+
-
GAIN
AMPLIFIER
SINGLE ENDED / DIFFERENTIAL SELECTION
10-BIT DAC
ADC CTRL. & STATUS A
REGISTER (ADCSRA)
ADC CONVERSION
COMPLETE IRQ
PRESCALER
CONVERSION LOGIC
INTERRUPT
TRIGGER
SELECT
FLAGS
SAMPLE & HOLD
COMPARATOR
15
+
-
ADC DATA REGISTER
(ADCH/ADCL)
ADC MULTIPLEXER
OUTPUT
ATA8742
0
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