Phase-locked loop circuit and voltage-controlled oscillator capable of producing oscillations in a plurality of frequency ranges
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsJingo Nakanishi, Yasunobu Nakase
Life of this patent
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Abstract
In a PLL circuit including a plurality of VCOs, first and second switches are respectively connected between the gate and source and the gate and drain of a P channel MOS transistor included in a current mirror circuit of each VCO. In a VCO which is employed, only the second switch is turned on to allow a control current to flow. In a VCO which is not employed, only the first switch is turned on to cut off the control current. Compared with a conventional circuit in which all of the plurality of VCOs are always producing oscillations, the power consumption is reduced.
Claims17
A phase-locked loop circuit generating a clock signal in synchronization with a reference clock signal, comprising:
- a phase difference detecting circuit detecting a difference in phase between said reference clock signal and said clock signal and supplying current according to the difference in phase;
- a control voltage generating circuit integrating the current supplied from said phase difference detecting circuit to generate a control voltage;
- a plurality of voltage-controlled oscillators respectively having different frequency ranges of oscillations that can be produced and each producing oscillations at a frequency according to said control voltage;
- a control circuit activating a voltage-controlled oscillator selected from said plurality of voltage-controlled oscillators and inactivating at least one other voltage-controlled oscillator;
- and
- a selecting circuit selecting and outputting oscillations produced by the voltage-controlled oscillator activated by said control circuit, said clock signal being supplied to said phase difference detecting circuit based on the selected oscillations;
- wherein
- said voltage-controlled oscillator includes:
- a current-controlled oscillator producing oscillations at a frequency according to a control current;
- a first transistor allowing current to flow according to said control voltage;
- and
- a current mirror circuit supplying current to said voltage-controlled oscillator as said control current according to the current flowing through said first transistor, and wherein
- said control circuit allows said current mirror circuit to stop its current transmitting function to inactivate said voltage-controlled oscillator and allows said current mirror circuit to perform its current transmitting function to activate said voltage-controlled oscillator.
A voltage-controlled oscillator producing oscillations at a frequency according to a control voltage comprising:
- a current-controlled oscillator producing oscillations at a frequency according to a control current;
- a first variable-resistance circuit connected between first and second nodes, and capable of varying a resistance value between the first and second nodes in response to a control signal;
- a transistor connected between the second node and a third node to allow current to flow according to said control voltage, said first variable-resistance circuit and said transistor being connected in series between the first node and the third node;
- and
- a current mirror circuit for supplying current to said current-controlled oscillator as said control current according to the current flowing through said transistor.
A voltage-controlled oscillator producing oscillations at a frequency according to a control voltage in a frequency range selected from a plurality of frequency ranges of oscillations that can be produced, comprising:
- a current-controlled oscillator producing oscillations at a frequency according to a control current;
- a first variable-resistance circuit having a resistance value adjusted according to said selected frequency range of oscillations that can be produced;
- a transistor connected in series with said first variable-resistance circuit to allow current to flow according to said control voltage;
- a current mirror circuit for supplying current to said current-controlled oscillator as said control current according to the current flowing through said transistor;
- a second variable-resistance circuit connected in parallel with said first variable-resistance circuit and said transistor and having its resistance value adjusted according to said selected frequency range of oscillations that can be produced, wherein
- said current mirror circuit supplies a sum of current flowing through said transistor and current flowing through said second variable-resistance circuit to said current-controlled oscillator.
A phase-locked loop circuit generating a clock signal in synchronization with a reference clock signal, comprising:
- a phase difference detecting circuit detecting a difference in phase between said reference clock signal and said clock signal and supplying current according to the difference in phase;
- a control voltage generating circuit integrating the current supplied from said phase difference detecting circuit to generate a control voltage;
- and
- a voltage-controlled oscillator having a plurality of selectable frequency ranges of oscillations that can be produced, producing oscillations at a frequency according to said control voltage in a frequency range of oscillations selected based on frequency of said reference dock signal, wherein
- said voltage-controlled oscillator includes:
- a current-controlled oscillator producing oscillations at a frequency according to a control current;
- a first variable-resistance circuit having its resistance value adjusted according to said selected frequency range of oscillations that can be produced;
- a first transistor connected in series with said first variable-resistance circuit and allowing current to flow according to said control voltage;
- and
- a current mirror circuit for supplying current to said current-controlled oscillator as said control current according to the current flowing through said first transistor.
Dependencies are inferred from the claim text.