In one form, a power supply monitor including a current controlled oscillator circuit, a time-to-digital converter, and an output divider. The current controlled oscillator circuit has an input for receiving a power supply voltage to be measured, and an output for providing a frequency signal having a frequency linearly proportional to the power supply voltage. The time-to-digital converter has an input coupled to the output of the current controlled oscillator circuit, and an output for providing a count signal representative of a number of cycles of a reference clock signal per cycle of the frequency signal. The output divider has an input coupled to the output of the time-to-digital converter, and an output for providing a divided count signal representative of a value of the power supply voltage, and provides the divided count signal by dividing a fixed number by the count signal.