Triple input phase detector and methodology for setting delay between two sets of phase outputs

Abstract

An improved clock generation circuit using a multi-phase phase-locked loop (PLL) circuit design that incorporates a dual set of PLLs. A first PLL maintains frequency lock control of an oscillator while a second PLL controls various phase outputs from delay circuits external to the oscillator which are locked in time delay with phase outputs from the oscillator. In this fashion, 2N phase outputs can be achieved with an oscillator that only produces N phase outputs. Furthermore, the second PLL uses a three-input phase detector that compares the phase output from one of the delay circuits external to the oscillator with a pair of phase outputs from the oscillator. Depending on the timing relationship of those output phases, the three-input phase detector will yield either a predominant pump-up pulse or a predominant pump-down pulse, through which the second PLL will use these signals to control the phase output of the external delay circuits relative to the phase outputs from the oscillator.