
172
8008H–AVR–04/11
ATtiny48/88
Figure 17-8. Analog Input Circuitry
Note:
The capacitor in the figure depicts the total capacitance, including the sample/hold capacitor and
any stray or parasitic capacitance inside the device. The value given is worst case.
17.9
Analog Noise Canceling Techniques
Digital circuitry inside and outside the device generates EMI which might affect the accuracy of
analog measurements. When conversion accuracy is critical, the noise level can be reduced by
applying the following techniques:
Keep analog signal paths as short as possible.
Make sure analog tracks run over the analog ground plane.
Keep analog tracks well away from high-speed switching digital tracks.
If any port pin is used as a digital output, it mustn’t switch while a conversion is in progress.
The analog supply voltage pin (AV
CC) should be connected to the digital supply voltage pin
(V
Figure 17-9. ADC Power Connections
ADCn
IIH
1..100 k
Ohm
CS/H= 14 pF
VCC/2
IIL
PD0
PC6
PC5
(ADC5/SCL)
PC4
(ADC4/SD
A)
PC
3
(ADC
3
)
PC2
(ADC2)
PC1 (ADC1)
PC0 (ADC0)
PA1 (ADC7)
GND
PC7
AVCC
PA0 (ADC6)
PB5
10
m
H
An
a
log
Gro
u
nd
Pl
a
n
e
100nF
VCC