Datasheet

28.6.2 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:

1. 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.

1.1. The AV

pin on the device should be connected to the digital V

supply voltage via an LC

network as shown in the figure below.

1.2. Use the ADC noise canceler function to reduce induced noise from the CPU.

1.3. If any ADC [3:0] port pins are used as digital outputs, it is essential that these do not switch

while a conversion is in progress. However, using the two-wire Interface (ADC4 and ADC5) will only

affect the conversion on ADC4 and ADC5 and not the other ADC channels.

Figure 28-9. ADC Power Connections

GND

VCC

PC5 (ADC5/SCL)

PC4 (ADC4/SDA)

PC3 (ADC3)

PC2 (ADC2)

PC1 (ADC1)

PC0 (ADC0)

ADC7

GND

AREF

AVCC

ADC6

PB5

10 µH

100 nF

Analog Ground Plane

ATmega48PA/88PA/168PA

Analog-to-Digital Converter (ADC)

Datasheet Complete

DS40002011A-page 322