This application note describes a technique for implementing an ADC for measuring both positive and negative input voltages while operating from a single (positive) supply.
This document describes a technique for implementing an Analog-to-Digital Converter (ADC) capable of measuring both positive and negative input voltages while operating from a single positive supply. The solution is based on a voltage-to-time conversion technique using an integrating capacitor, a resistor, an external op-amp, and comparators. It is designed to be compatible with ST7 microcontrollers, such as the ST72F264, utilizing their 16-bit timers for time measurement.
The converter is designed to measure both positive and negative input voltages while operating from a single positive supply.
The ST72F264 microcontroller is used as the example, though the implementation works with any ST7 microcontroller.
The circuit uses a 16-bit timer, but it can also work with a microcontroller equipped with an 8-bit timer.