Fast-acquisition phase-locked loop
AssigneeSkyworks Solutions, Inc.
InventorEvan S. McCarthy
Life of this patent
Estimating the term…
Abstract
The invention provides techniques for compensating for current leakage from a loop filter during off times of a PLL between on times of the PLL, e.g., when a cell phone is in paging mode. The leakage current is compensated by providing offsetting charge to ensure that the VCO tuning voltage when the PLL is turned from “off” to “on” is at or near the VCO tuning voltage when the PLL is locked (the VCO-lock voltage). Several techniques can be used compensate for the leakage current and several techniques can be used to determine how accurately the leakage current is being compensated for, and what, if any, adjustments to make in the offsetting charge to adequately compensate for the leakage current.
Claims61
A phase-locked loop (PLL) system having active times and inactive times, the system comprising:
- an apparatus configured to provide charge;
- a voltage-controlled oscillator (VCO) having a VCO input coupled and configured to receive charge from the apparatus, a tuning voltage at the VCO input being at a VCO-lock voltage when the phase-locked loop system is locked to a frequency;
- and
- a controller coupled to the apparatus and configured to provide a control signal to the apparatus to control the charge provided by the apparatus;
- wherein the apparatus is configured to provide, during at least a portion of an inactive time of the PLL system and in response to the control signal, charge such that the tuning voltage at the VCO input is approximately at the VCO-lock voltage at the start of an active time of the PLL system.
A method comprising:
- activating a phase-locked loop (PLL), including a voltage-controlled oscillator (VCO), to lock onto a frequency, a tuning voltage of the VCO being at a VCO-lock voltage when the PLL is locked;
- determining a difference between the tuning voltage approximately at an activation time of the PLL and the VCO-lock voltage;
- deactivating the PLL;
- and
- providing charge, in an amount depending upon the difference, to the VCO during at least a portion of a deactivation time when the PLL is deactivated to affect the tuning voltage of the VCO.
A phase-locked loop (PLL) comprising:
- a voltage-controlled oscillator (VCO) having a VCO input, a tuning voltage at the VCO input being at a VCO-lock voltage when the PLL is locked to a frequency;
- means for determining an indication of a difference between the tuning voltage approximately at an activation time of the PLL and the VCO-lock voltage;
- and
- means for providing charge, in an amount depending upon the indication, to the VCO during at least a portion of a deactivation time when the PLL is deactivated to affect the tuning voltage of the VCO.
A portable telephone comprising:
- a battery;
- an antenna;
- and
- a receiver coupled to the antenna and to the battery and including a phase-locked loop (PLL) configured to operate in an active mode and a paging mode, the paging mode intermittently activating the PLL to check as to whether an incoming call is being received, the PLL including:
- a charge supply;
- a voltage-controlled oscillator (VCO) having a VCO input coupled and configured to receive charge from the charge supply, a tuning voltage at the VCO input being at a VCO-lock voltage when the phase-locked loop system is locked to a frequency;
- and
- a controller configured to determine a total amount of charge to provide to the VCO input during a deactivated time period of the PLL to cause the tuning voltage to be approximately equal to the VCO-lock voltage at a beginning of an active time period of the PLL, the controller being further configured to cause the charge supply to provide the total amount of charge to the VCO during at least a portion of the deactivated time period of the PLL.
A method comprising:
- activating at least a charge pump of a phase-locked loop (PLL) system;
- receiving indicia of initial charge to provide by the charge pump to cause a tuning voltage of a voltage-controlled oscillator (VCO) to become at least approximately equal to a VCO-lock voltage from a deactivation steady state of the PLL system, the tuning voltage of the VCO being at the VCO-lock voltage when the PLL system is locked to a frequency;
- causing the charge pump to provide the initial charge;
- and
- activating the PLL system when the VCO tuning voltage is approximately equal to the VCO-lock voltage such that the PLL system attempts to lock to a frequency.
Dependencies are inferred from the claim text.