Patent ID: 6163185
Filing Date: 2000-12-19
Classification: H03L

Abstract:
A digital phase-frequency detector comprising:detection means for detecting phase and frequency differences between a first digital signal at a first input of said digital phase-frequency detector and a second digital signal at a second input of said digital phase-frequency detector, said detection means providing an up signal if said first digital signal leads said second digital signal and a down signal if said first digital signal lags said second digital signal;output means for providing a detector output signal that represents an instantaneous phase error between said first and second digital signals, said output means being controlled by said up and down signals, said output means comprising at least one capacitor for providing said output signal as an instantaneously detected signal, and said output means comprising a first sourcing current source and a first current sinking source, and switching means for switching said first sourcing current source to said at least one capacitor during presence of said up signal and for switching said first sinking current source to said at least one capacitor during presence of said down signal, said up signal charging said at least one capacitor and said down signal discharging said at least one capacitor.