I have a microcontroller with a built in ADC that I am using to read from an input pin (ATMEGA328P to be specific). I want to allow switching of resolutions on the input for our users (0-5V range, and 0-10V range) which i was planning on doing via a voltage divider. The thing I'm worried about is if the user has our unit in 0-5V mode and plugs in a higher voltage by mistake. I want some sort of overvoltage protection on the output of the voltage divider to protect my ADC. I don't care if this is a crowbar circuit that doesn't reset without removing power, anything that protects the unit will do. I'm open to all suggestions. Thanks!
Electronic – How should I protect from overvoltage ADC
adcanalogvoltage divider
Related Solutions
Use the voltage divider with resistors, and an opamp follower afterwards. Alternative use an opamp circuit to reduce the voltage and you can perform anti alias filtering in one stage!
A simple pair of diodes is all you need. One from the ADC input to \$V_{CC}\$, anode on \$V_{CC}\$. One from the ADC input to GND, cathode to GND.
If \$V_{in}\$ goes above \$V_{CC}\$ then the excess will go through the upper diode. If it falls below GND then it will flow through the lower diode. The input to the ADC will be just the range between \$V_{CC}\$ and GND.
Most ADC inputs will have these diodes in them already - check the data sheet - but it can't hurt to have your own extra ones.
Shottky diodes would be best as they switch faster than normal silicon ones.
Best Answer
You can use a non-inverting comparator op-amp such that the basic configuration for the circuit detects when the input signal, VIN is ABOVE or more positive than the reference voltage, VREF producing an output at VOUT which is HIGH as shown.
credits go to : electronics-tutorials.com
With the help of a NPN you can pull the voltage applied to the ADC Pin down to zero by using this circuit " one of my designs "