A low-power voltage controlled oscillator is provided. The voltage controlled oscillator includes (2n+1) first circuit components (n is an integer of one or more). An output terminal of the first circuit component in a k-th stage (k is an integer of one or more and 2n or less) is connected to an input terminal of the first circuit component in a (k+1)-th stage. An output terminal of the first circuit component in a (2n+1)-th stage is connected to an input terminal of the first circuit component in a first stage. One of the first circuit components includes a second circuit component and a third circuit component whose input terminal is connected to an output terminal of the second circuit component. The third circuit component includes a first transistor and a second transistor whose source-drain resistance is controlled in accordance with a signal input to a gate through the first transistor.

A phase discontinuity mitigation implementation within a phased lock loop (PLL) improves throughput of a radio access technology. The throughput is improved by maintaining a phase of the PLL while powering off some devices of the PLL, such as a local oscillator (LO) frequency divider. In one instance, when the PLL is powered down, one or more portions of a delta sigma modulator for the PLL are clocked with a reference clock for the PLL. This implementation maintains phase continuity when the first phase lock loop turns back on.

A phase-locked loop (PLL) performs hitless switching from a first reference clock (ref1) to a second reference clock (ref2) by entering holdover mode (418), and aligning the feedback clock (fbclk) to the second reference clock while in holdover mode. The alignment is performed by adjusting a divisor input (D) for the multi-mode divider (128) that divides the output clock frequency (PLLout) to generate the feedback clock. Other features are also provided.

A phase-locked loop (PLL) performs hitless switching from a first reference clock (ref1) to a second reference clock (ref2) by entering holdover mode (418), and aligning the feedback clock (fbclk) to the second reference clock while in holdover mode. The alignment is performed by adjusting a divisor input (D) for the multi-mode divider (128) that divides the output clock frequency (PLLout) to generate the feedback clock. Other features are also provided.

A digital phase locked loop includes a digital phase detector, a digital loop filter, a digital controlled oscillator, a first divider that divides the second frequency of the oscillation signal depending on a first division value and outputs the division result as a division signal having a third frequency, a second divider that divides the second frequency of the oscillation signal depending on a second division value and outputs the division result as an output signal having a final frequency, a dithering block that receives the division signal and performs dithering on the first division value based on a preset pattern as cycles of the division signal pass, and a digital phase domain filter that performs second low pass filtering on the division signal in a phase domain and outputs the result of the second low pass filtering as the feedback signal.

A digital phase locked loop includes a digital phase detector, a digital loop filter, a digital controlled oscillator, a first divider that divides the second frequency of the oscillation signal depending on a first division value and outputs the division result as a division signal having a third frequency, a second divider that divides the second frequency of the oscillation signal depending on a second division value and outputs the division result as an output signal having a final frequency, a dithering block that receives the division signal and performs dithering on the first division value based on a preset pattern as cycles of the division signal pass, and a digital phase domain filter that performs second low pass filtering on the division signal in a phase domain and outputs the result of the second low pass filtering as the feedback signal.

Generation of a clock signal in a semiconductor integrated circuit (IC) is controlled using a Noise Modulation Agent (NMA), configured to measure the clock signal and output a parameter indicative of an effective cycle time of the clock signal. An Adaptive Frequency Scaling (AFS) circuit selectively adjusts a frequency of the clock signal, based on the output of the NMA indicating a change in a power supply voltage of the semiconductor IC.

A phase discontinuity mitigation implementation within a phased lock loop (PLL) improves throughput of a radio access technology. The throughput is improved by maintaining a phase of the PLL while powering off some devices of the PLL, such as a local oscillator (LO) frequency divider. In one instance, when the PLL is powered down, one or more portions of a delta sigma modulator for the PLL are clocked with a reference clock for the PLL. This implementation maintains phase continuity when the first phase lock loop turns back on.

An electronic circuit is described including an oscillator generating an oscillating signal having a cycle responsive to an input signal, a voltage detector producing a detection signal responsive to a power supply voltage, a frequency divider generating a frequency-divided signal obtained by dividing a frequency of the oscillating signal by a frequency-division ratio responsive to the detection signal, and an adder obtaining a sum of a first signal and a second signal and to supply a signal responsive to the sum to the oscillator as the input signal. The first signal is responsive to a difference in phase between the frequency-divided signal and a reference signal, and the second signal is responsive to the detection signal. A related method is also described.

Generation of a clock signal in a semiconductor integrated circuit (IC) is controlled using a Noise Modulation Agent (NMA), configured to measure the clock signal and output a parameter indicative of an effective cycle time of the clock signal. An Adaptive Frequency Scaling (AFS) circuit selectively adjusts a frequency of the clock signal, based on the output of the NMA indicating a change in a power supply voltage of the semiconductor IC.