I want to read a voltage from 0-30V with an MCU ADC which has a maximum input of 3V.
Initially I thought of using a 100k-10k divider (so 33V translates to 3V) but according to the answers to ADC input impedance on MCUs, this will add a 3% error due to the input leakage current; I'm looking for 0.5% error maximum. However, at lower values for the divider, I risk damaging the MCU's inputs because of overvoltage (the resistors act in tandem with the clamping diodes on the input.) I also increase power dissipation in my resistors, which are tiny 0603 devices, rated for 0.063W maximum. How can I avoid this? n.b. input impedence is not critical.
I'm not worried about sampling speed, it will be monitoring a battery voltage at a maximum of 100 samples per second.