An analog-to-digital converter (ADC) is provided. The ADC includes a variable oscillator, a frequency divider, a clock circuit, and a counter. The variable oscillator is coupled to a sensor and configured to generate an oscillating signal based on a measurement generated by the sensor. The frequency divider is coupled to the variable oscillator and configured to divide a frequency of the oscillating signal. The clock circuit is configured to generate a clock signal at a defined frequency. The counter is coupled to the frequency divider and to the clock and is configured to generate a bit stream representative of a first number of periods of the clock signal during a second number of periods of the divided oscillating signal.