Disclosed as a clock alignment module for a near field communication, NFC, controller operable in active load modulation, ALM, card mode, the module being operable during a transmit mode comprising transmit bursts and comprising: an input for receiving a field clock signal (CLK_FIELD); an output for outputting a local controller clock signal (CLK_FB); a transmit envelop unit configured to determine whether a time since an end of a latest transmit burst exceeds a threshold, Tdelay; and a phase locked loop, PLL, configured to selectively lock the phase of the local controller clock signal to the phase of the field clock signal, in response to the time exceeding the threshold and a next transmit burst not having started. Associated NFC controllers, integrated circuits and methods are also disclosed.

A phase correcting device includes a local oscillator that includes an all digital phase-locked loop configured to output a local oscillation signal, a first phase detector configured to detect a phase of the local oscillation signal to output the phase of the local oscillation signal, a reference phase device configured to generate a quasi-reference phase corresponding to a reference phase of the local oscillation signal to output the quasi-reference phase, based on a reference clock, a second phase detector configured to detect a fluctuation amount of a phase of the local oscillator, based on the phase detected by the first phase detector and the quasi-reference phase, and a correction circuit configured to correct the phase of the inputted signal by using a detection result of the second phase detector.

A phase correcting device includes a local oscillator configured to give a local oscillation signal to a device configured to detect a phase of an inputted signal, a first phase detector configured to detect a phase of the local oscillation signal to output the phase of the local oscillation signal, a reference phase device configured to generate a quasi-reference phase corresponding to a reference phase of the local oscillation signal at a time of an initial setting of the local oscillator to output the quasi-reference phase, based on a reference clock, a second phase detector configured to detect a fluctuation amount of a phase of the local oscillator, based on the phase detected by the first phase detector and the quasi-reference phase, and a correction circuit configured to correct the phase of the inputted signal by using a detection result of the second phase detector.

An oscillator including a switched capacitor configured to generate a sawtooth or ramp voltage in response to a switched capacitor drive signal; a low pass filter (LPF) configured to filter the sawtooth or ramp voltage to generate a filtered voltage; a reference voltage generator configured to generate a reference voltage; an integrator configured to integrate a difference between the sawtooth or ramp voltage and the reference voltage to generate a frequency control signal; a voltage controlled oscillator (VCO) configured to generate a first clock based on the frequency control signal; a frequency divider configured to frequency divide the first clock to generate a second clock; and a switched capacitor driver configured to generate the switched capacitor drive signal in response to the second clock. The oscillator may also include a switched capacitor sampler to sample the sawtooth or ramp voltage, wherein the filtered voltage is based on the sampled voltage.

Techniques are described for accurate tracking of a radiofrequency (RF) carrier for amplitude-modulated signals in unstable reference clock environments. For example, some embodiments operate in context of clock circuits in devices configured for near-field communication (NFC) card emulation (CE) mode. The clock circuits seek to generate an internal clocking signal by tracking a clock reference, such as an RF carrier. In some cases, the clock reference can unpredictably become unreliable for periods of time, during which continued tracking of the unreliable clock reference can yield appreciable frequency and phase errors in the generated internal clocking signal. Embodiments implement phase delta detection with time limiting to limit the magnitude of such errors in the internal clocking signal introduced while tracking an unreliable clock reference. For example, embodiments force gating of phase tracking signals to limit their duration, thereby limiting impacts of those phase tracking signals on the clock circuit output.

A phase locked loop (PLL) system for mitigating non-linear phase errors stemming from time-variant integral non-linearity of the LO feedback phase quantizer (TDC) is disclosed. The system includes a phase modulation circuit which is configured to generate a plurality of phase shifts for a reference signal; select a phase shift of the plurality of phase shifts and introduce the selected phase shift into the reference signal, thereby modulating the phase difference between the feedback and the reference signal. Alternatively, the above phase modulation can be applied on the feedback signal path, attaining equivalent results. TDC is configured to quantize the phase of the LO feedback signal relative to the shifted reference signal to generate a phase detection signal, effectively modulating the non-linearity contributed error away from the LO center frequency. The phase detection signal is then digitally compensated for the intentional fractional frequency shift to allow the PLL to generate LO signal the desired frequency.

An apparatus includes a first function module providing a master signal, a second function module providing a comparison signal, and safety logic. The safety logic includes a toggle signal generator having a comparator providing a comparison result in response to the master signal and the comparison signal, a feedback path generating a first toggle signal in response to the comparison result and providing a feedback signal to the comparator, and a first multiple input gate generating a second toggle signal in response to the comparison result. The safety logic also includes a toggle signal monitor providing a final fault search signal in response to the first toggle signal and the second toggle signal.

A system includes a digital phase-locked loop (DPLL) having a loop filter and a digitally-controlled oscillator (DCO). The system also includes a clock generator coupled to an output of the DPLL, and a plurality of clock domains coupled to the clock generator. The DPLL is configured to transition between a low power mode and a normal mode, wherein the loop filter is configured to maintain its value when the DPLL transitions from the normal mode to the low power mode. The DCO is configured to output a DCO clock signal based on the maintained loop filter value when the DPLL transitions from the low power mode to the normal mode.

A system and method to dynamically control a reset signal for an IQ divider are provided. The system includes an IQ divider configured to output a IQ divider output clock; an input configured to receive a reference clock; a failure sensing circuit configured to sense a failure in the IQ divider output clock, the failure sensing circuit including an automatic frequency calibration (AFC) logic; and a control circuit configured to control a reset signal provided to the IQ divider, based on an output of the failure sensing circuit corresponding the failure sensed by the failure sensing circuit.

Embodiments of the present disclosure describe methods, apparatuses, and systems for phase-lock loop (PLL) configuration and realization to provide various reference clock frequencies to computing core(s) and processor(s), and other benefits. A post digitally-controlled oscillator (DCO) divider (PDIV) of the PLL may be configured with a dedicated PDIV threshold value corresponding to a dedicated target reference frequency.