Hallo, I want to measure analog signals with an ATMega328. For a better use of measurement range, I switch to external reference and connect the AREF pin to a voltage lower then 5 V (e.g. 1.1 V). The analog signal is from a RTD. The RTD is fed by a constant current source. For normal conditions all is fine. But if the RTD is damaged (resistance grow up like open RDT connection line), the constant current source rise up to a maximum value of 2.5 V. Is that a problem for the ATMega, if on the analog IN is a voltage level higher than the voltage an AREF pin? additional question: Same question but in case of use the internal reference (like in ATMega 2560). Thank you.