Abstract: A system that generates a click signal includes a first digitally controlled oscillator (DCO) having a first fundamental frequency, and a second DCO having a second fundamental frequency. The system also includes a Muller C-element, which combines outputs of the first and second DCOs to produce the clock signal, which feeds back into the first and second DCOs. During a calibration operation, while the second DCO is set to a frequency larger than the target frequency, the system adjusts the first DCO with reference to a first feedback loop, which includes the first DCO, so that the clock signal matches the target frequency, and while the first DCO is set to the adjusted first fundamental frequency plus a frequency offset, the system adjusts the second DCO with reference to a second feedback loop, which includes the second DCO, so that the clock signal matches the target frequency.

Abstract: In an integrated circuit that provides a clock signal, an asymmetric frequency-locked loop (AFLL) includes a first digitally controlled oscillator (DCO) that outputs a first signal having a first fundamental frequency, and a second DCO that outputs a second signal having a second fundamental frequency. The integrated circuit includes a voltage regulator that provides a power-supply voltage to the second DCO. Moreover, the AFLL includes control logic that selects one of the first DCO and the second DCO based on an instantaneous value of a power-supply voltage and an average power-supply voltage. Furthermore, the AFLL adjusts a gain of the selected DCO in the first sub-frequency-locked loop based on the instantaneous value of the power-supply voltage and the average power-supply voltage. In this way, an impact of power-supply voltage variations on a time-critical path in the integrated circuit is reduced.

Abstract: In an integrated circuit that provides a clock signal, an asymmetric frequency-locked loop (AFLL) includes a first digitally controlled oscillator (DCO) that outputs a first signal having a first fundamental frequency, and a second DCO that outputs a second signal having a second fundamental frequency. The integrated circuit includes a voltage regulator that provides a power-supply voltage to the second DCO. Moreover, the AFLL includes control logic that selects one of the first DCO and the second DCO based on an instantaneous value of a power-supply voltage and an average power-supply voltage. Furthermore, the AFLL adjusts a gain of the selected DCO in the first sub-frequency-locked loop based on the instantaneous value of the power-supply voltage and the average power-supply voltage. In this way, an impact of power-supply voltage variations on a time-critical path in the integrated circuit is reduced.