Phase-locked loop calibration system
AssigneeSequoia Communications
InventorsJohn Groe, Carrie Lo
Life of this patent
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Abstract
Phase locked loop calibration system. Apparatus is provided for calibration of a phase-locked loop. The apparatus includes logic to calibrate an integration filter of the phase-locked loop, and logic to calibrate a charge pump current of the phase-locked loop, wherein the integration filter and charge pump current are calibrated to achieve a desired phase-locked loop performance level.
Claims13
Apparatus for calibration of a phase-locked loop including a frequency divider, the apparatus comprising:
- logic to automatically calibrate an integration filter of the phase-locked loop based on a predefined filter transfer function, wherein said calibration is independent of the frequency divider parameters and the integration filed is calibrated by setting the value of one or more components of the integration filter to achieve a desired RC product set to achieve a predefined RC time constant, wherein the components include a resistive component and a capacitive component and the resistive component is set to achieve the desired RC product based on the value of the capacitive component, and wherein the logic to automatically calibrate an integration filter includes:
- a plurality of resistive elements;
- a plurality of switches configured to couple ones of the plurality of resistive elements to a charging current circuit;
- a first transistor coupled to a first of the plurality of resistive elements;
- an amplifier circuit coupled to the first transistor, said amplifier circuit configured to fix a charging current based on a reference voltage;
- and
- logic to automatically calibrate a charge pump current of the phase-locked loop, wherein the integration filter and charge pump current are calibrated to achieve a desired phase-locked loop performance level.
A method for precision calibration of a phase locked loop comprising the steps of:
- automatically calibrating the pole and zero locations of a phase locked loop integration filter to a desired transfer function;
- and
- automatically calibrating the charge pump current of a charge pump circuit based at least in part on the calibrated pole and zero location parameters, wherein said charge pump calibration is based on a desired transfer function;
- wherein said automatically calibrating the pole and zero locations of a phase locked loop integration filter to a desired transfer function comprises:
- setting a variable resistive element of the integration filter to a first value;
- comparing an RC time constant of the variable resistive element and a capacitive element to a reference time constant;
- and
- adjusting the value of the variable resistive element responsive to said comparing.
A method for calibrating a phase-locked loop, comprising:
- setting a resistor value of a resistor component of an integration filter of the PLL to establish a predefined RC time constant for the integration filter;
- and
- adjusting, after setting the resistor value, the open-loop gain of the PLL to replicate a control voltage step of a VCO component of the PLL developed at a first VCO frequency and a second VCO frequency.
Dependencies are inferred from the claim text.