The operating characteristics of a dynamic comparator is used to automatically change the resolution of a sloped or ramped analog-to-digital converter (ADC) by switching the comparator on and off between first (slow) and second (fast) clock frequencies and comparing the amplitude of a sampled input signal against a ramp input signal. The slow clock frequency is first used to determine the area of interest, while the fast clock frequency is then used to zoom into a high resolution area of interest.