Phase-lock loop startup circuit and voltage controlled oscillator reference generator
First Claim
1. A method of startup for a phase-locked loop (PLL), the method comprising:
- at initiation of the PLL, providing a reference voltage from a startup voltage source to an input of a voltage controlled oscillator (VCO) in the PLL, wherein the reference voltage is set to a predetermined minimum voltage;
stepwise increasing the reference voltage from the predetermined minimum voltage;
comparing a frequency of a reference signal input to the PLL with a frequency of a feedback signal originating from an output of the VCO of the PLL to determine a frequency differential as the reference voltage increases;
determining whether a convergence criterion is met according to the frequency differential;
while the convergence criterion is not met, increasing the reference voltage; and
when the convergence criterion is met, replacing the reference voltage provided by the startup voltage source with an operational voltage generated by an operational voltage source.
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Abstract
A method of startup for a phase-locked loop (PLL) can include, at initiation of the PLL, providing a reference voltage from a startup voltage source to an input of a voltage controlled oscillator (VCO) in the PLL, wherein the reference voltage is set to a predetermined minimum voltage. The reference voltage can be stepwise increased from the predetermined minimum voltage. A frequency of a reference signal input to the PLL can be compared with a frequency of a feedback signal originating from an output of the VCO of the PLL to determine a frequency differential as the reference voltage increases. A determination can be made as to whether a convergence criterion is met according to the frequency differential. While the convergence criterion is not met, the reference voltage can be increased. When the convergence criterion is met, the reference voltage provided by the startup voltage source can be replaced with a voltage generated by an operational voltage source.
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Citations
20 Claims
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1. A method of startup for a phase-locked loop (PLL), the method comprising:
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at initiation of the PLL, providing a reference voltage from a startup voltage source to an input of a voltage controlled oscillator (VCO) in the PLL, wherein the reference voltage is set to a predetermined minimum voltage; stepwise increasing the reference voltage from the predetermined minimum voltage; comparing a frequency of a reference signal input to the PLL with a frequency of a feedback signal originating from an output of the VCO of the PLL to determine a frequency differential as the reference voltage increases; determining whether a convergence criterion is met according to the frequency differential; while the convergence criterion is not met, increasing the reference voltage; and when the convergence criterion is met, replacing the reference voltage provided by the startup voltage source with an operational voltage generated by an operational voltage source. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A phase-locked loop (PLL) system comprising a voltage controlled oscillator (VCO) and a voltage reference generator, wherein the reference voltage generator comprises:
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a reference voltage source that, at initiation of the PLL system, generates a reference voltage set to a predetermined minimum voltage that is provided to an input of the VCO in the PLL system; and a controller that stepwise increases the reference voltage of the reference voltage source, compares a frequency of a reference signal provided to the PLL system with a frequency of a feedback signal originating from an output of the VCO, calculates a frequency differential between the reference signal and the feedback signal as the reference voltage increases, and determines whether a convergence criterion is met according to the frequency differential, wherein, when the convergence criterion is met, the controller disconnects the reference voltage source from the input of the VCO and connects an operational voltage source to the input of the VCO. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A phase-locked loop (PLL) system, comprising:
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an operational voltage source that generates an operational voltage that is provided to an input of a voltage controlled oscillator (VCO) of the PLL system during phase and frequency lock of the PLL system; a reference voltage source generating a reference voltage; and a controller that, while the PLL system is in phase and frequency lock, determines whether a reference signal to the PLL system is available and controls the reference voltage source to generate the reference voltage approximating the operational voltage from the operational voltage source, wherein the controller selectively stores a count value, indicating the reference voltage, in memory, wherein, responsive to determining that the reference signal is unavailable, the controller operationally disconnects the operational voltage source from the input of the VCO, recalls the count value from memory, controls the reference voltage source to generate the reference voltage having a voltage corresponding to the recalled count value, and operationally connects the reference voltage source to the input of the VCO. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification