Voltage-controlled oscillator and phase-locked loop

Abstract

The invention discloses a voltage-controlled oscillator and a phase-locked loop, which can equivalently provide a high-voltage-controlled oscillator gain for the slow change of an input voltage so asto increase the tolerance to processes, temperatures, voltages and the like, and equivalently provide a low-voltage-controlled oscillator gain for the fast change of the input voltage so as to reducejitter. One embodiment of the voltage-controlled oscillator comprises an input circuit used for generating an input current according to an input voltage; a first current supply circuit used for generating a first output current according to the input current; a second current supply circuit used for generating a second output current according to the input current; a filter coupled with the inputcircuit and the second current supply circuit, and used for reducing the influence speed of the change of the input current on the second current supply circuit; and an oscillating circuit used for generating an output frequency according to the first output current and the second output current.

Description

technical field [0001] The present invention relates to an oscillator and a phase-locked loop, and in particular to a voltage-controlled oscillator and a phase-locked loop using the voltage-controlled oscillator or its equivalent. Background technique [0002] The jitter (ie phase noise) of the output signal of a PLL reflects the output performance of the PLL. Based on the same input noise, the output jitter of the phase-locked loop of the VCO with smaller gain is smaller. Therefore, in order to realize a low-jitter PLL, a low-gain VCO is necessary. [0003] However, the oscillating frequency of the VCO is affected by process, temperature, and voltage, and the low-gain VCO has low tolerance to the above effects. In order to prevent the output frequency of the voltage-controlled oscillator from being seriously affected, it is known that the low-gain voltage-controlled oscillator will be equipped with an additional frequency correction circuit to eliminate the variation of t...

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Problems solved by technology

[0003] However, the oscillation frequency of the voltage-controlled oscillator will be affected by the process, temperature, and voltage, and the low-gain voltage-controlled oscillator is less tolerant to the above-mentioned effects

In order to prevent the output frequency of the voltage-controlled oscillator from being seriously affected, it is known that the low-gain voltage-controlled oscillator will be equipped with an additional frequency correction circuit to eliminate the variation of the process, but the frequency offset caused by the change of temperature and voltage is still It may make the output frequency of the voltage controlled oscillator exceed the expected range. Since most systems using the phase locked loop do not allow the phase locked loop to set aside time to re-calibrate the frequency during normal operation, the gain of the voltage controlled oscillator cannot be constant. ambiguity is reduced to reduce jitter, at least large enough to cover temperature and voltage variations

[0004] Based on the above, although high-gain VCOs are more tolerant to the influence of process, temperature, and voltage, however, as product specifications set stricter jitter requirements, high-gain VCOs must use huge loops filter to meet the jitter requirement, the loop filter must even be implemented by an external capacitor on the chip, which leads to an increase in circuit area and cost

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