ATMEGA644PV ATMEL [ATMEL Corporation], ATMEGA644PV Datasheet - Page 248

• Manufacturer Part Number: ATMEGA644PV
• Description: 8-bit Microcontroller with 16/32/64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

21.7.2
21.7.3
248
ATmega164P/324P/644P
Analog Noise Canceling Techniques
Offset Compensation Schemes
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 21-9. 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.
a. Keep analog signal paths as short as possible. Make sure analog tracks run over the
b. The AVCC pin on the device should be connected to the digital V
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
analog ground plane, and keep them well away from high-speed switching digital
tracks.
via an LC network as shown in
switch while a conversion is in progress.
Figure
21-9.
PA4 (ADC4)
PA5 (ADC5)
PA6 (ADC6)
PA7 (ADC7)
AREF
GND
AVCC
PC7
CC
supply voltage
8011D–AVR–02/07