SENA Rhio10 - Manual (Page 41)

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2) When using an Analog Input Potentiometer
An analog input operates in reference to input voltage and has an impedance of 100㏀. When
using a Potentiometer as shown in Figure 4-9, an impedance in the range of 1㏀ - 5㏀ is ideal.
When using an external signal source, lower impedance ensures stable operation against
various noises.
Note: Make sure that analog Input voltage does not exceed AREF voltage.
Figure 4-9 Circuit connection when a Potentiometer is used
3) Connecting when a voltage higher than AVCC voltage is used
For voltage input, the circuit should be split as shown in Figure 4-10. In case that the input wire
is long or there is a strong noise nearby, it is recommended to have additional clamp diode in
order to minimize the effect to other ADC channels although there is an internal clamp diode
available.
Figure 4-10 Circuit connection when a voltage higher than Avcc is used