A phase detector generates a phase dependent control signal according to
the phase relationship between a first and second clock signal. The phase
detector includes first and second phase detector circuits receiving the
first and second clock signals and generating select signals having duty
cycles corresponding to the phase relationship between the clock edges of
the first and second clock signals. The phase detector also includes a
charge pump that receives select signals from the phase detector circuits
and produces an increasing or decreasing control signal when the first
and second clock signals do not have the predetermined phase
relationship, and a non-varying control signal when the first and second
clock signals do have the predetermined phase relationship. The control
signal may be used to adjust the delay value of a voltage-controlled
delay circuit in order to adjust the phase relationship between the first
and second clock signals to have a predetermined phase relationship.