ATxmega128A3 Atmel Corporation, ATxmega128A3 Datasheet - Page 292

• Manufacturer Part Number: ATxmega128A3
• Manufacturer: Atmel Corporation

Specifications of ATxmega128A3

• Flash (kbytes): 128 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 32 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 50
• Ext Interrupts: 50
• Usb Speed: No
• Usb Interface: No
• Spi: 10
• Twi (i2c): 2
• Uart: 7
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 16
• Adc Resolution (bits): 12
• Adc Speed (ksps): 2000
• Analog Comparators: 4
• Resistive Touch Screen: No
• Dac Channels: 2
• Dac Resolution (bits): 12
• Temp. Sensor: Yes
• Crypto Engine: AES/DES
• Sram (kbytes): 8
• Eeprom (bytes): 2048
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.6 to 3.6
• Operating Voltage (vcc): 1.6 to 3.6
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 7
• Output Compare Channels: 22
• Input Capture Channels: 22
• Pwm Channels: 22
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

25.3.3
25.3.4
8077H–AVR–12/09
Single ended input
Internal inputs
For single ended measurements all analog input pins can be used as inputs. Single ended mea-
surements can be done in both signed and unsigned mode.
The negative input is connected to internal ground in signed mode.
Figure 25-4. Single-ended measurement in signed mode
In unsigned mode the negative input is connected to half of the voltage reference (VREF) volt-
age minus a fixed offset. The nominal value for the offset is:
Since the ADC is differential, unsigned mode is achieved by dividing the reference by two inter-
nally, resulting in an input range from VREF to zero for the positive single ended input. The
offset enables the ADC to measure zero cross detection in unsigned mode, and to calibrate any
positive offset where the internal ground in the device is higher than the external ground. See
Figure 25-11 on page 296
Figure 25-5. Single ended measurement in unsigned mode
Four internal analog signals can be selected as input and measured by the ADC.
The voltage output from an internal temperature reference can be measured with the ADC and
the voltage output will give an ADC result representing the current temperature in the microcon-
troller. During production test, the ADC measures a fixed temperature using the internal
• Temperature sensor
• Bandgap voltage
• V
• DAC output
CC
scaled
ADC0
ADC1
ADC2
ADC3
ADC4
ADC5
ADC6
ADC7
ADC0
ADC1
ADC2
ADC3
ADC4
ADC5
ADC6
ADC7
for details.
ΔV
VREF
=
2
VREF 0.05
−
Δ
V
×
+
-
+
-
ADC
ADC
XMEGA A
292