Arduino protecting analog input with internal voltage reference Usually a common way to protect an analog input consists on reducing voltage and current in the following way:

Current limiting components, as Resistors or inductors and voltage limiting components as diodes, zener, tvs.

In this case for components availability I have used two resistors and a zener diode.

The circuits aims to accept a 0-10V input and read it with the internal reference voltage 1,1V.

The question is the following: Assuming I want to use a 2,2V zener diode as overvoltage protection and 1,1V internal voltage reference, can I consider it safe or the 2,2V of zener will be too much for the 1,1V reference?   







simulate this circuit &ndash; Schematic created using CircuitLab

NOTES: I am using 2,2V zener diode because is the smallest size I can found.
I could use two normal diodes to reach 1,4V but maybe it will be too much for 1,1V reference and the result could be the same.
I could also add an external reference, but I would like to know if I can have problems with this configuration.
Yes, it is safe.  The reference voltage is only used as a comparison. The ADC is still powered by, and limited by, the chip's supply voltage (5V).

The AREF voltage has no bearing on what limits there are on voltages you can apply to a pin. All that will happen is that voltages above 1.1V will register as 1023. You can go right up to 5V safely.