Systems and methods for sensing voltage on a chip are described herein. In one embodiment, a voltage sensor comprises a voltage-controlled oscillator coupled to a voltage being sensed, and a plurality of transition detectors, wherein each of the transition detectors is coupled to a different location on the oscillator, and wherein each of the transition detectors is configured to count a number of transitions at the respective location over a time period. The voltage sensor also comprises an adder configured to add the numbers of transitions from the transition detectors to generate an output value that is approximately proportional to the voltage.