ATMEGA169P_0611 Datasheet, PDF (222/390 Pages) ATMEL Corporation – 8-bit Microcontroller with 16K Bytes In-System Programmable Flash

21.7.2
Analog Noise Canceling Techniques
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:
a. Keep analog signal paths as short as possible. Make sure analog tracks run over the
analog ground plane, and keep them well away from high-speed switching digital
tracks.
b. The AVCC pin on the device should be connected to the digital V_CC supply voltage
via an LC network as shown in Figure 21-9.
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
switch while a conversion is in progress.
Figure 21-9. ADC Power Connections
PA0 51
VCC ₅₂
GND
53
(ADC7) PF7 54
(ADC6) PF6 55
(ADC5) PF5 56
(ADC4) PF4 57
(ADC3) PF3 58
(ADC2) PF2 59
(ADC1) PF1 60
(ADC0) PF0 61
10μΗ
AREF 62
GND ₆₃
AVCC ₆₄
100nF
1
Ground Plane
222 ATmega169P
8018I–AVR–11/06