Redundant clock source
AssigneeHewlett-Packard Development Company, L.P.
InventorDaniel Wissell
Life of this patent
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Abstract
A redundant clock source provides a stable clock source for digital system. The clock source uses two oscillators to generate a clock signal. If one of the oscillators fails, the clock signal is generated from the other oscillator until the failed oscillator is replaced. Special filtering of the waveforms produced by the oscillators makes the clock source is resistant to jitter from the oscillators and transients that occur when an oscillator fails. This allows the clock source to not only use a redundant oscillator in an attempt to eliminate a single point of failure, but to also provide a stable clock signal even if one oscillator fails.
Claims14
A clock system comprising:
- first and second oscillators having the same frequency;
- a circuit for coupling a first waveform derived from said first oscillator and a second waveform derived from said second oscillator to produce a third waveform, said circuit comprising a first filter to receive the output of said first oscilator to produce said first waveform;
- a resonant filter connected to receive said third waveform and generate clock edges;
- and
- an output buffer connected to receive said clock edges and generate a master clock signal.
A clock system comprising:
- a first oscillator configured to produce a first signal;
- a first filter for converting said first signal to a first waveform;
- a second oscillator configured to produce a second waveform;
- a multiplexer receiving said first and second waveforms as inputs;
- means for choosing an output of said multiplexer from said first and second waveforms;
- a buffer connected to receive a waveform chosen by said means for choosing;
- and
- a band pass filter connected to said buffer to receive the chosen waveform, the bandpass filter configured to generate a clock signal from the chosen waveform.
A method of producing a clock signal in a redundant clock system comprising:
- deriving first and second waveforms from a first and second oscillators, said oscillators having a same frequency, wherein said first waveform differs from said second waveform;
- coupling said first and second waveforms to produce a third waveform;
- and
- filtering said third waveform with a resonant filter to produce clock edges;
- and
- passing said clock edges to an output buffer, said output buffer generating a master clock signal.
A method of producing a clock signal in a redundant clock system comprising:
- deriving first and second waveforms from a first and second oscillators, said oscillators having a same frequency, said first waveform being different than said second waveform;
- receiving said first and second waveforms as inputs of a multiplexer;
- choosing an output of said multiplexer from said first and second waveforms;
- and
- passing a waveform chosen by said multiplexer though a resonant filter to produce a third waveform.
A clock system comprising:
- first and second oscillators having the same frequency, the first oscillator producing a first waveform and the second oscillator producing a second waveform, wherein said first waveform is different than said second waveform;
- a summer coupled to the first and second oscillators, the summer configured to produce a third waveform from the first and second waveforms;
- a resonant filter connected to the summer to receive said third waveform and generate clock edges;
- and
- an output buffer connected to receive said clock edges and generate a master clock signal.
Dependencies are inferred from the claim text.