ATMEGA644A-PU Atmel, ATMEGA644A-PU Datasheet - Page 242

• Manufacturer Part Number: ATMEGA644A-PU
• Description: IC MCU AVR 64K FLASH 40PDIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644A-PU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• Processor Series: ATmega
• Core: AVR
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: JTAG, TWI, SPI, USART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 32
• Number Of Timers: 3
• Operating Supply Voltage: 3.3 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 22-1. Analog-to-digital Converter Block Schematic
22.3
8272A–AVR–01/10
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.
164A/164PA/324A/324PA/644A/644PA/1284/1284P
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
CONVERSION LOGIC
+
-
ADTS[2:0]
START
TRIGGER
SELECT
SAMPLE & HOLD
INTERRUPT
COMPARATOR
ADC
MULTIPLEXER
OUTPUT
FLAGS
15
ADC DATA REGISTER
(ADCH/ADCL)
0
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