Split Transformer Based LC-Tank Oscillator

摘要

A novel and useful LC-tank digitally controlled oscillator (DCO) incorporating a split transformer configuration. The LC-tank oscillator exhibits a significant reduction in area such that it is comparable in size to conventional ring oscillators (ROs) while still retaining its salient features of excellent phase noise and low sensitivity to supply variations. The oscillator incorporates an ultra-compact split transformer topology that is less susceptible to common-mode electromagnetic interference than regular high-Q LC tanks which is highly desirable in SoC environments. The oscillator, together with a novel dc-coupled buffer, can be incorporated within a wide range of circuit applications, including clock generators and an all-digital phase-locked loop (ADPLL) intended for wireline applications.

主权项

1. An oscillator, comprising:
a passive LC-tank circuit having an input and an output; an active circuit coupled to said passive circuit, said active circuit having an input coupled to the output of said passive circuit and an output coupled to the input of said passive circuit; said passive circuit comprising a split transformer whose primary windings are coupled between said active circuit outputs and whose secondary windings are coupled between said active circuit inputs; and wherein said split transformer is configured so as to substantially cancel their respective magnetic fields.