A current-controlled oscillator receives an input current. Ramp voltage generating circuitry generates first and second ramp voltages in response to the input current. Selecting circuitry selects one of the first and second ramp voltages depending on their relative values. Switching circuitry receives a selected ramp voltage, generates a signal based on the selected ramp voltage relative to a reference voltage, and outputs a clock signal. In one embodiment, a comparator receives the reference voltage, one of the first and second ramp voltages, and outputs a comparison signal. Logic circuitry controls the ramp voltage generating circuitry to output one of the ramp voltages during one half of a clock cycle and to output the other ramp voltage during another half cycle of the clock signal based on the comparison signal and logic states of the logic circuitry.