Low power charge pump

A charge pump comprising:

• a current switch for generating a first control signal responsive to a second control signal and a bias signal;
• and
• a bias cell coupled to the current switch for generating the bias signal;
• wherein the bias cell can be controllably enabled and disabled so as to enable and disable the current switch, thereby reducing the power consumption of the charge pump;
• wherein the second control signal includes a first direction signal and a second direction signal, and the first control signal sources a first current responsive to the first direction signal and sinks a second current responsive to the second direction signal;
• and
• wherein the current switch includes:
• a first current source coupled to the bias cell to generate the first current responsive to the bias signal;
• a first switch coupled to the first current source to enable the charge pump to source the first current responsive to the first direction signal;
• a current mirror coupled to the first switch to mirror the first current;
• a second current source coupled to the bias cell to generate the second current responsive to the bias signal;
• and
• a second switch coupled to the second current source to enable the charge pump to sink the second current responsive to the second direction signal.

A charge pump comprising:

• a current switch for generating a first control signal responsive to a second control signal and a bias signal;
• and
• a bias cell coupled to the current switch for generating the bias signal;
• wherein the bias cell can be controllably enabled and disabled so as to enable and disable the current switch, thereby reducing the power consumption of the charge pump;
• and
• wherein the bias cell generates a second bias signal which can be deactivated responsive to an enable signal.

A method for generating an oscillating signal comprising:

• locking the oscillating signal;
• enabling a charge pump for generating a control signal when the control signal needs to be generated;
• disabling the charge pump when the control signal does not need to be generated, thereby reducing the power consumption of the charge pump;
• generating a reference signal;
• generating a reference look-ahead signal which is activated before the reference signal is activated;
• and
• enabling the charge pump responsive to the reference look-ahead signal;
• wherein the charge pump is intermittently enabled and disabled while the oscillating signal is locked.

A frequency synthesizer comprising:

• a frequency generator for generating an oscillating signal;
• a charge pump coupled to the frequency generator for cyclically updating the frequency generator;
• a detector circuit coupled to the frequency generator and the charge pump for controlling the charge pump responsive to the oscillating signal and a reference signal so as to lock the oscillating signal with the reference signal;
• a control circuit coupled to the charge pump for disabling the charge pump during a portion of each update cycle;
• and
• a divider coupled between the frequency generator and the detector for dividing the oscillating signal, thereby generating a variable signal;
• wherein the control circuit enables the charge pump responsive to either the reference signal or the variable signal and disables the charge pump responsive to a reset signal from the detector circuit.

A method for locking an oscillating signal comprising:

• generating the oscillating signal responsive to the state of a filter;
• detecting the difference between the oscillating signal and a reference signal;
• cylically updating the filter with a charge pump responsive to the difference between the oscillating signal and a reference signal;
• disabling the charge pump during a portion of each update cycle;
• dividing the oscillating signal, thereby generating a variable signal;
• enabling the charge pump when the first of either the reference pulse or the variable pulse occurs during each update cycle;
• and
• enabling the charge pump prior to the occurrence of either the reference pulse or the variable pulse, thereby allowing the charge pump to stabilize;
• wherein a reference pulse occurs in the reference signal during each update cycle, and a variable pulse occurs in the variable signal during each update cycle;
• and
• wherein enabling the charge pump prior to the occurrence of either the reference pulse or the variable pulse includes:
• generating a reference look-ahead signal responsive to the reference signal;
• generating a variable look-ahead signal responsive to the variable signal;
• and
• enabling the charge pump responsive to the reference look-ahead signal or the variable look-ahead signal.