Phase-locked loop apparatus and tuning voltage providing circuit thereof
AssigneeNovatek Microelectronics Corp.
InventorHsiang-Chi Li
Life of this patent
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Abstract
A phase-locked loop apparatus (PLL apparatus) and a tuning voltage providing circuit thereof are provided. The PLL apparatus is for receiving an input signal and producing an output signal according to the received input signal. The PLL apparatus includes a voltage-controlled oscillator (VCO), a loop filter and a tuning voltage providing circuit. The VCO receives a control voltage and produces the output signal according to the received control voltage. The loop filter has a resistor-capacitor network and the network receives the control voltage and is coupled to a reference voltage. The tuning voltage providing circuit receives the output signal and the input signal and provides a tuning voltage to the resistor-capacitor network according to the input signal and the output signal.
Claims20
A phase-locked loop apparatus, receiving an input signal and producing an output signal according to the received input signal;
- the phase-locked loop apparatus comprising:
- a voltage-controlled oscillator, receiving a control voltage and producing the output signal according to the received control voltage;
- a loop filter, coupled between the voltage-controlled oscillator and a reference voltage and receiving the control voltage;
- and
- a tuning voltage providing circuit, coupled to the loop filter and the voltage-controlled oscillator, further receiving the output signal and the input signal and providing a tuning voltage to the loop filter according to the input signal and the output signal,
- wherein the tuning voltage providing circuit judges whether or not the frequency ratio between the input signal and the output signal is greater than a locked threshold to decide whether or not provide the tuning voltage.
A tuning voltage providing circuit, used for coupling a loop filter of a phase-locked loop apparatus, wherein the loop filter is coupled to a voltage-controlled oscillator for receiving a control voltage;
- the tuning voltage providing circuit comprising:
- a lock detection circuit, producing a lock signal according to an input signal and an output signal of the phase-locked loop apparatus;
- a control signal generator, coupled to the lock detection circuit, receiving the lock signal and producing a control signal according to the lock signal;
- and
- a voltage-providing buffer, coupled between the control signal generator and the loop filter, receiving the control signal and the tuning voltage and deciding whether or not to provide a tuning voltage to the loop filter according to the control signal.
Dependencies are inferred from the claim text.