PHASE DELAY LOOP COMPRISING A CONTROL UNIT CAPABLE OF VARYING THE NUMBER OF DELAY UNITS OF A VOLTAGE CONTROLLED DELAY LINE AND ITS METHOD OF ORDERING THE SAME

摘要

Phase locked loop integrated circuits include a phase detection circuit, a variable delay device and a delay control circuit. The variable delay device and delay control circuit provide improved characteristics by increasing the signal frequency bandwidth of the delay locked loop integrated circuit in a preferred manner. The phase detection circuit is configured to perform the functions of comparing first and second periodic signals and generating a phase control signal (e.g., VCON) having a first property (e.g., magnitude) that is proportional to a difference in phase between the first and second periodic signals. The delay control circuit is responsive to the phase control signal VCON and generates a delay control signal that is provided to the variable delay device. The delay control circuit may comprise a counter, a first comparator, a second comparator and a shift register. The variable delay device includes a variable delay line and a compensation delay device. The variable delay line may contain a string of unit delay devices and a string of switches that each have an input electrically coupled to an output of a corresponding unit delay device. Each of the unit delay devices in the string may provide a fixed delay or a variable delay that is influenced (e.g., increased) by changes (e.g., increases) in the magnitude of the phase control signal VCON.