Apple Inc.
Multi-stage clock generator using mutual injection for multi-phase generation

Abstract:

A multi-stage clock generation circuit is disclosed. The circuit includes first and second ring oscillators. The ring oscillators include a corresponding plurality of delay elements coupled in series, with a plurality of shunt circuits in parallel with corresponding inverters. The shunt circuits include respective interpolation nodes, which are resistively coupled to input and output nodes of their corresponding inverters. The interpolation nodes of the first ring oscillator are coupled to delay element input and output nodes of the second ring oscillator. Similarly, the interpolation nodes of the second ring oscillator are coupled to delay element input and output nodes of the first ring oscillator.