Analog Input Protection Circuit

Analog input pins are a common feature of many microcontroller boards. However, due to the operating voltage of the board, you are limited to a maximum analog input voltage (1.8V, 3.3V, 5V), beyond which you will end up frying your board. But that low voltage range is pretty restrictive if you would like to apply some of the functionality of a microcontroller to a measurement outside that range. To get around this, you can create an analog input protection circuit to allow you to make measurements on higher voltages, while minimizing the risk of frying your pin or whole board. Here I will go over the design method I used to create a voltage divider and diode clamp to protect an analog input pin on a uC32 microcontroller, but these concepts can be applied to creating a circuit for any board. A basic knowledge of circuit theory and analog components would be helpful in understanding what is going on, but is not strictly necessary to just follow along.”


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