ATMEGA328P_14 Datasheet, PDF (250/344 Pages) ATMEL Corporation – ATMEL 8-BIT MICROCONTROLLER WITH 4/8/16/32KBYTES

Figure 23-8. Analog Input Circuitry
ADCn
I_IH
I_IL
1..100 kΩ
C_S/H= 14 pF
V_CC/2
23.6.2
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:
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 AV_CC pin on the device should be connected to the digital V_CC supply voltage via
an LC network as shown in Figure 23-9.
c. Use the ADC noise canceler function to reduce induced noise from the CPU.
d. 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 2-wire Interface (ADC4
250 Atmel ATmega328P [Preliminary]
7810C–AVR–10/12