ATxmega128B1 Atmel Corporation, ATxmega128B1 Datasheet - Page 327

• Manufacturer Part Number: ATxmega128B1
• Manufacturer: Atmel Corporation

Specifications of ATxmega128B1

• Flash (kbytes): 128 Kbytes
• Pin Count: 100
• Max. Operating Frequency: 32 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 53
• Ext Interrupts: 53
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 3
• Twi (i2c): 1
• Uart: 2
• Segment Lcd: 160
• 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
• 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: 3
• Output Compare Channels: 10
• Input Capture Channels: 10
• Pwm Channels: 10
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

25.4
25.5
8291A–AVR–10/11
Sampling Time Control
Voltage Reference Selection
is lower than that of the ADC. Refer to the ADC characteristics in the device datasheets for
details.
For differential measurement Pad Ground (Gnd) and Internal Gnd can be selected as negative
input. Pad Gnd is the gnd level on the pin and identical or very close to the external gnd. Internal
Gnd is the internal device gnd level.
Internal Gnd is used as the negative input when other internal signals are measured in single-
ended signed mode.
Figure 25-6. Internal measurements in single-ended signed mode.
To measure the internal signals in unsigned mode, the negative input is connected to a fixed
value given by the formula below, which is half of the voltage reference (VREF) minus a fixed
offset, as it is for single-ended unsigned input. Refer to
VINN = VREF/2 - ΔV
Figure 25-7. Internal measurements in unsigned mode.
To support applications with high source output resistance, the sampling time can be increased
by steps of a half ADC clock cycle.
The following voltages can be used as the reference voltage (VREF) for the ADC:
• Accurate internal 1.00V voltage generated from the bandgap
• Internal V
• Internal V
• External voltage applied to AREF pin on PORTA
•
External voltage applied to AREF pin on PORTB
CC
CC
BANDGAP REF
/1.6V voltage
/2V voltage
VCC SCALED
TEMP REF
BANDGAP REF
VCC SCALED
TEMP REF
VREF
2
−
Δ
V
Atmel AVR XMEGA B
Figure 25-11 on page 329
+
-
ADC
+
-
for details.
327