ATxmega32D4 Atmel Corporation, ATxmega32D4 Datasheet - Page 229

• Manufacturer Part Number: ATxmega32D4
• Manufacturer: Atmel Corporation

Specifications of ATxmega32D4

• Flash (kbytes): 32 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 32 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 34
• Ext Interrupts: 34
• Usb Speed: No
• Usb Interface: No
• Spi: 4
• Twi (i2c): 2
• Uart: 2
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 12
• Adc Resolution (bits): 12
• Adc Speed (ksps): 200
• Analog Comparators: 2
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 4
• Eeprom (bytes): 1024
• 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: 4
• Output Compare Channels: 14
• Input Capture Channels: 14
• Pwm Channels: 14
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

20.4
20.5
8210B–AVR–04/10
Voltage reference selection
Conversion Result
The following voltages can be used as the voltage reference (VREF) for the ADC:
•
•
•
•
Figure 20-8. ADC voltage reference selection
The ADC can be set up to be either in signed or in unsigned mode.
In signed mode, both negative and positive voltages can be measured, both for single ended
and differential input. With 12-bit resolution, the TOP value of a signed result is 2047 and the
results will be in the range -2048 to +2047 (0xF800 - 0x07FF). In unsigned mode the TOP value
is 4095 and results will be in the range 0 - 4095 (0 - 0x0FFF).
Signed mode must be used when any of the ADC inputs are set up for differential measure-
ments. In unsigned mode only single ended or internal signals can be measured.
The result of the analog to digital conversion is written to the result registers, RES.
In signed mode the ADC transfer function can be written as:
VINP and VINN are the positive and negative inputs to the ADC. GAIN is 1 unless differential
measurement with gain is used.
In unsigned mode the ADC transfer functions can be written as:
VINP is the single ended or internal input.
The application software selects if an 8- or 12-bit result should be generated. A result with lower
resolution will be available faster. See the
a description on how to calculate the propagation delay for.
The result register is 16-bit. An 8-bit result is always represented right adjusted in the 16-bit
result registers. Right adjusted means that the 8 LSB is found in the low byte. A 12-bit result can
Accurate internal 1.00 V voltage.
Internal V
External voltage applied to AREF pin on PORTA.
External voltage applied to AREF pin on PORTB.
RES
RES
=
CC
VINP - VINN
-------------------------------- - GAIN TOP
/1.6 voltage.
=
VREF
VINP - (-ΔV )
--------------------------------- - TOP
VREF
⋅
⋅
Internal VCC/1.6
Internal 1.00V
⋅
AREFA
AREFB
”ADC Clock and Conversion Timing” on page 231
VREF
XMEGA D
229
for