ATmega1280 Atmel Corporation, ATmega1280 Datasheet - Page 283

• Manufacturer Part Number: ATmega1280
• Manufacturer: Atmel Corporation

Specifications of ATmega1280

• Flash (kbytes): 128 Kbytes
• Pin Count: 100
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 86
• Ext Interrupts: 32
• Usb Speed: No
• Usb Interface: No
• Spi: 5
• Twi (i2c): 1
• Uart: 4
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 16
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 8
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 6
• Output Compare Channels: 16
• Input Capture Channels: 4
• Pwm Channels: 15
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

26.5.2
26.6
2549N–AVR–05/11
ADC Noise Canceler
ADC Voltage Reference
The reference voltage for the ADC (V
ended channels that exceed V
either AVCC, internal 1.1V reference, internal 2.56V reference or external AREF pin.
AVCC is connected to the ADC through a passive switch. The internal 1.1V reference is gener-
ated from the internal bandgap reference (VBG) through an internal amplifier. In either case, the
external AREF pin is directly connected to the ADC, and the reference voltage can be made
more immune to noise by connecting a capacitor between the AREF pin and ground. V
also be measured at the AREF pin with a high impedant voltmeter. Note that V
impedant source, and only a capacitive load should be connected in a system. The Internal
2.56V reference is generated from the 1.1V reference.
If the user has a fixed voltage source connected to the AREF pin, the user may not use the other
reference voltage options in the application, as they will be shorted to the external voltage. If no
external voltage is applied to the AREF pin, the user may switch between AVCC, 1.1V and
2.56V as reference selection. The first ADC conversion result after switching reference voltage
source may be inaccurate, and the user is advised to discard this result.
If differential channels are used, the selected reference should not be closer to AVCC than
indicated in
The ADC features a noise canceler that enables conversion during sleep mode to reduce noise
induced from the CPU core and other I/O peripherals. The noise canceler can be used with ADC
Noise Reduction and Idle mode. To make use of this feature, the following procedure should be
used:
Note that the ADC will not be automatically turned off when entering other sleep modes than Idle
mode and ADC Noise Reduction mode. The user is advised to write zero to ADEN before enter-
ing such sleep modes to avoid excessive power consumption.
If the ADC is enabled in such sleep modes and the user wants to perform differential conver-
sions, the user is advised to switch the ADC off and on after waking up from sleep to prompt an
extended conversion to get a valid result.
1. Make sure that the ADC is enabled and is not busy converting. Single Conversion
2. Enter ADC Noise Reduction mode (or Idle mode). The ADC will start a conversion
3. If no other interrupts occur before the ADC conversion completes, the ADC interrupt
mode must be selected and the ADC conversion complete interrupt must be
enabled.
once the CPU has been halted.
will wake up the CPU and execute the ADC Conversion Complete interrupt routine. If
another interrupt wakes up the CPU before the ADC conversion is complete, that
interrupt will be executed, and an ADC Conversion Complete interrupt request will be
generated when the ADC conversion completes. The CPU will remain in active mode
until a new sleep command is executed.
“ADC Characteristics – Preliminary Data” on page
REF
ATmega640/1280/1281/2560/2561
will result in codes close to 0x3FF. V
REF
) indicates the conversion range for the ADC. Single
377.
REF
can be selected as
REF
is a high
REF
283
can