Datasheet

ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
214
21.5.2 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 21-9.
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 and ADC5) will only affect the conversion on ADC4 and
ADC5 and not the other ADC channels.
Figure 21-9. ADC Power Connections
GND VCC PC5 (ADC5/SCL) PC4 (ADC4/SDA) PC3 (ADC3) PC2 (ADC2)
PC1 (ADC1)
Analog Ground Plane
PA0 (ADC0)
ADC7
GND
100nF 10μH
AVCC
ADC6
AREF
PB5