Datasheet

224
8018P–AVR–08/10
ATmega169P
22.7.2 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 22-9.
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 22-9. ADC Power Connections
VCC
GND
100 nF
Ground Plane
(ADC0) PF0
(ADC7) PF7
(ADC1) PF1
(ADC2) PF2
(ADC3) PF3
(ADC4) PF4
(ADC5) PF5
(ADC6) PF6
AREF
GND
AVCC
52
53
54
55
56
57
58
59
60
6161
6262
6363
6464
1
51
LCDCAP
PA0
10 µH