A circuit includes a level-crossing detector to generate a level-crossing detection signal when an input signal crosses a predetermined voltage level. A first stage set of capacitors is operatively coupled to the level-crossing detector. A ramp circuit is operatively coupled to the set of series-connected capacitors. A second stage set of capacitors is operatively coupled to the first stage set of capacitors and the ramp circuit. The ramp circuit includes a feedback capacitor and a preset switch to provide a linear ramp output.