A circuit, which is usable in a flash analog-to-digital converter, includes a first switch configured to provide a first reference voltage to a first reference node responsive to a first control signal and a second switch configured to provide the first reference voltage to a second reference node responsive to a second control signal. A third switch is coupled to the first switch and is configured to provide a second reference voltage to the first reference node responsive to a clock signal. Further, a fourth switch is coupled to the second switch and configured to provide the second reference voltage to the second reference node responsive to the clock signal.