ATMEGA48-20MJ Atmel, ATMEGA48-20MJ Datasheet - Page 244

• Manufacturer Part Number: ATMEGA48-20MJ
• Description: IC AVR MCU 4K 5V 20MHZ 32-QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA48-20MJ

• 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: 23
• Program Memory Size: 4KB (2K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-VQFN Exposed Pad, 32-HVQFN, 32-SQFN, 32-DHVQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ATMEGA48-24MJ; ATMEGA48-24MJ

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ATmega48/88/168
Figure 23-1. Analog to Digital Converter Block Schematic Operation
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.
The ADC generates a 10-bit result which is presented in the ADC Data Registers, ADCH and
ADCL. By default, the result is presented right adjusted, but can optionally be presented left
adjusted by setting the ADLAR bit in ADMUX.
If the result is left adjusted and no more than 8-bit precision is required, it is sufficient to read
ADCH. Otherwise, ADCL must be read first, then ADCH, to ensure that the content of the Data
Registers belongs to the same conversion. Once ADCL is read, ADC access to Data Registers
is blocked. This means that if ADCL has been read, and a conversion completes before ADCH is
AREF
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
AVCC
GND
INTERNAL 1.1V
REFERENCE
REFERENCE
BANDGAP
8-BIT DATA BUS
INPUT
MUX
ADC MULTIPLEXER
SELECT (ADMUX)
MUX DECODER
10-BIT DAC
ADC CTRL. & STATUS
REGISTER (ADCSRA)
ADC CONVERSION
COMPLETE IRQ
CONVERSION LOGIC
PRESCALER
SAMPLE & HOLD
COMPARATOR
15
+
-
ADC DATA REGISTER
(ADCH/ADCL)
ADC MULTIPLEXER
OUTPUT
2545S–AVR–07/10
0