Phase detector with linear output response

Abstract

A parallel sampling phase detector with linear output response is disclosed. The parallel sampling phase detector is disclosed for use in data recovery. The device includes a voltage controlled oscillator (VCO) that generates ten separate phase signals using a five stage ring oscillator. Five linear phase detectors are employed in the device, each operating during one of five 'window' intervals. The 'window' intervals are non-overlapping, and are generated using preselected ones of the VCO output phases. The linear phase detectors each generate, respectively, a variable pulsewidth pump up signal wherein the pulsewidth of the pump up signal is proportional to a phase difference between the input data signal applied to the phase detector, and the output phase signals of the VCO. Each phase detector also generates a pump down signal that has a fixed pulsewidth. A loop filter determines the difference between the pump up and pump down signals and develops a control signal to vary the output frequency and phase of the VCO in accordance therewith. Each phase detector also operates as a deserializer, capturing, during the interval when the respective 'window' signal is active, the data signal from the input data stream. The plurality of sampled data signals are captured by a data register, which then outputs an n-bit (5-bit) parallel format data word. The linear phase detector includes means for generating the pump down signal in response to the generation of the pump up signal.