Ring VCO based on RC timing
AssigneeTropian, Inc.
InventorYves Dufour
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Abstract
The present invention, generally speaking, provides a controlled oscillator that attains the foregoing objectives. The structure of the oscillator is, in general, that of a ring; however, timing of the oscillator is governed largely by an RC time constant. Since the delay is mostly RC-based, phase noise is minimal compared to an active implementation. Furthermore, in a preferred embodiment, two ring oscillators of this type are combined to form a differential oscillator circuit having still lower phase noise. In an exemplary embodiment, the ring oscillators are three-stage ring oscillators. The operation of two inverters is unaffected by the RC time constant. Because the speed of these inverters is very fast compared to the RC time constant, the oscillation frequency is quite constant versus temperature and supply voltage.
Claims5
A controlled oscillator, comprising:
- at least one ring oscillator comprising:
- an odd number of inverter stages coupled together in a ring configuration, each inverter stage having an output terminal and at least one input terminal and comprising a pull-up device and a pull-down device;
- for at most one of the inverter stages:
- an RC network coupled within a current path of one of the pull-up device and the pull-down device of the one inverter stage and coupled to an output terminal of the one inverter stage;
- and
- a control input signal coupled to said one of the pull-up device and the pull-down device of the one inverter stage, an other one of the pull-up device and the pull-down device of the one inverter stage being coupled to an output terminal of a preceding inverter stage in the ring configuration.
Dependencies are inferred from the claim text.