Charge pump with transient current correction
AssigneeInternational Business Machines Corporation
InventorDavid William Boerstler
Life of this patent
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Abstract
An improved charge pump used in a phase-locked loop includes transient current correction capability by adding a canceling capacitance for each parasitic capacitance associated with a switching device in a charge pump. For each transient current component flowing through the parasitic capacitance, a canceling capacitance is implemented to create a canceling transient current component in the opposite direction such that it cancels out the transient current component. Preferably, an additional switching device is added to implement such a canceling capacitance for each parasitic capacitance.
Claims20
A charge pump coupled to a loop filter to charge and discharge the loop filter in a phase-locked loop, the charge pump comprising:
- a first switching device configured for receiving a first control signal, the first switching device having at least a first parasitic capacitance such that a first transient current component is created across the first parasitic capacitance while the first control signal is in a transient state;
- and
- a first canceling capacitance coupled to the first parasitic capacitance and configured for receiving an inverted signal of the first control signal such that a first canceling transient current component is created across the first canceling capacitance while the first control signal in a transient state, thereby effectively canceling out the first transient current component.
A phase-locked loop comprising:
- a phase-frequency detector generating one or more control signals;
- a charge pump coupled to the phase-frequency detector for receiving the one or more control signal, the charge pump comprising:
- a first switching device configured for receiving a first control signal, the first switching device having at least a first parasitic capacitance such that a first transient current component is created across the first parasitic capacitance while the first control signal is in a transient state;
- and
- a first canceling capacitance coupled to the first parasitic capacitance and configured for receiving an inverted signal of the first control signal such that a first canceling transient current component is created across the first canceling capacitance while the first control signal in a transient state, thereby effectively canceling out the first transient current component;
- a loop filter coupled to the charge pump and configured for generating a voltage output Vc;
- and
- a voltage-controlled oscillator coupled to the loop filter for receiving the voltage output Vc and configured for generating an output signal.
Dependencies are inferred from the claim text.