A gated phase-frequency detector circuit includes a phase-frequency
detector and a multiplexer circuit. The phase-frequency detector is
arranged to provide UP and DOWN signals responsive to a reference clock
signal and a feedback signal. Further, the phase-frequency detector
includes a first flip-flop that provides the UP signal, a second
flip-flop that provides the DOWN signal, and a clear logic circuit. One
input of the multiplexer circuit is coupled to the output of the first
flip-flop, another input of the multiplexer circuit is arranged to
receive a logic high signal, and an output of the multiplexer circuit is
coupled to the D input of the first flip-flop. The multiplexer circuit is
arranged to multiplex the logic high signal and the UP signal responsive
to a reference gate signal. If the reference gate signal corresponds to
an active level, logic level of the UP signal does not change.