atmega32u4-16mu ATMEL Corporation, atmega32u4-16mu Datasheet - Page 321

• Manufacturer Part Number: atmega32u4-16mu
• Description: Atmega32u4 8-bit Avr Microcontroller With 32k Bytes Of Isp Flash And Usb Controller
• Manufacturer: ATMEL Corporation

25.7.2
25.7.3
25.7.4
7766A–AVR–03/08
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 25-10. ADC Power Connections
Note:
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 same circuitry should be used for AVCC filtering on the ADC8-ADC13 side
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
(ADC1) PF1
(ADC0) PF0
25-10.
AVCC
AREF
GND
GND
VCC
34
35
36
37
38
39
40
41
42
43
44
1
ATmega32U4
n
-1.
CC
supply voltage
REF
in 2
n
steps
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