Patent ID: 6049233
Filing Date: 2000-04-11
Classification: H03D,H03L

Abstract:
An improved phase detection apparatus for generating a difference signal for use in a phase locked loop, the phase detection apparatus having a first storage circuit and a second storage circuit each having a reset input and an output, the first storage circuit having a clock input configured to receive a reference clock signal and the second storage circuit having a clock input configured to receive a variable clock signal, wherein the improvement comprises:a first charge pump coupled to the output of the first storage circuit to provide an up current in response to a first output signal from the first storage circuit;a first delay circuit coupled to the output of the first storage circuit for producing a delayed output signal in response to the output signal from the first storage circuit;a second charge pump coupled to the output of the second storage circuit to provide a down current in response to a second output signal from the second storage circuit;a circuit which combines the delayed output signal and the second output signal to produce a reset signal; anda second delay circuit which delays the reset signal to produce a delayed reset signal, the second delay circuit being coupled to the reset input of the first storage circuit and the second storage circuit.