AT90USB647 Atmel Corporation, AT90USB647 Datasheet - Page 322

• Manufacturer Part Number: AT90USB647
• Manufacturer: Atmel Corporation

Specifications of AT90USB647

• Flash (kbytes): 64 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 48
• Ext Interrupts: 16
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device + OTG
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 4
• Eeprom (bytes): 2048
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 4
• Output Compare Channels: 10
• Input Capture Channels: 1
• Pwm Channels: 9
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

25.6.2
25.6.3
25.6.4
322
AT90USB64/128
Analog Noise Canceling Techniques
Offset Compensation Schemes
ADC Accuracy Definitions
Digital circuitry inside and outside the device generates EMI which might affect the accuracy of
analog measurements. If conversion accuracy is critical, the noise level can be reduced by
applying the following techniques:
Figure 25-9. ADC Power Connections
The gain stage has a built-in offset cancellation circuitry that nulls the offset of differential mea-
surements as much as possible. The remaining offset in the analog path can be measured
directly by selecting the same channel for both differential inputs. This offset residue can be then
subtracted in software from the measurement results. Using this kind of software based offset
correction, offset on any channel can be reduced below one LSB.
An n-bit single-ended ADC converts a voltage linearly between GND and V
(LSBs). The lowest code is read as 0, and the highest code is read as 2
Several parameters describe the deviation from the ideal behavior:
a. Keep analog signal paths as short as possible. Make sure analog tracks run over
b. The AV
c. Use the ADC noise canceler function to reduce induced noise from the CPU.
d. If any ADC port pins are used as digital outputs, it is essential that these do not
the analog ground plane, and keep them well away from high-speed switching digi-
tal tracks.
via an LC network as shown in
switch while a conversion is in progress.
CC
pin on the device should be connected to the digital V
Analog Ground Plane
100nF
Figure
(ADC7) PF7
(ADC6) PF6
(ADC5) PF5
(ADC4) PF4
(ADC3) PF3
(ADC2) PF2
(ADC1) PF1
(ADC0) PF0
(AD0) PA0
25-9.
AREF
AVCC
GND
GND
VCC
51
52
53
54
55
56
57
58
59
60
61
61
62
62
63
63
64
64
1
n
-1.
CC
supply voltage
REF
7593K–AVR–11/09
in 2
n
steps