Various aspects of this disclosure describe switched-capacitor circuits in a PLL. Examples include routing current from a first current source through a capacitor to ground during a first clock phase, routing current from a second current source through the capacitor to ground during a second clock phase, and transferring charge on the capacitor to a loop filter capacitor during a third clock phase. The first current source may generate current responsive to UP error samples from a phase/frequency detector (PFD), and the second current source generates current responsive to DN error samples from the PFD.

Systems and methods are provided for a phase locked loop. A phase/frequency detector is configured to receive a reference signal and a feedback signal. A charge pump is configured to receive outputs from the phase/frequency detector and to generate pulses. An oscillator is configured to generate an output waveform based on the charge pump pulses. A realignment path is configured to generate a clock realignment signal that is provided to the oscillator based on the outputs from the phase/frequency detector.

A start-up phase of a phase lock loop (PLL) circuit includes supplying, by a phase comparator, of control pulses during which an output signal frequency of an oscillator increases. The increase includes an application of a pre-charge current at the oscillator input. A determination is made of a time variation of the output signal frequency. At least one adjustment is made of the intensity of the pre-charge current depending on the at least one determined time variation so as to approach a reference time variation.

Some embodiments include apparatuses having a first path in a phase locked loop, the first path including a phase frequency detector to receive a first signal having a first frequency and a first node to provide a voltage; an oscillator coupled to a second node and the first node to provide a second signal having a second frequency at the second node; a second path including a frequency divider coupled to the second node and the phase frequency detector; and a circuit to generate digital information having a value based on a value of the voltage at the second node.

A successive-approximation register (SAR) analog-to-digital converter (ADC) circuit includes a comparator circuit and a plurality of latch circuits. The comparator circuit is configured to compare an analog signal with a plurality of reference levels. The latch circuits, coupled to the comparator circuit and connected in series, are triggered sequentially in response to a plurality of trigger signals, respectively, to store a comparator output of the comparator circuit and accordingly generate a digital signal. A first latch circuit and a second latch circuit of the latch circuits are triggered in response to a first trigger signal and a second trigger signal of the trigger signals, respectively. The first latch circuit is configured to generate the second trigger signal according to the comparator output stored in the first latch circuit.

There is configured a charge pump circuit for outputting a phase difference current to a first node, the charge pump circuit including a first current source coupled between a high potential power supply node and the first node, a second current source coupled between a low potential power supply node and the first node, a first switch coupled between the first current source and the first node, a second switch coupled between the second current source and the first node, a third switch coupled between the first current source and a second node, a fourth switch coupled between the second current source and the second node, a third current source for supplying a negative offset current to the first node, and a push-type differential amplifier circuit an input side of which is coupled to the first node, and an output side of which is coupled to the second node.

An apparatus is disclosed for a charge pump with voltage tracking. In an example aspect, the apparatus includes a locked loop having a charge pump, a filter, a second switch, and a buffer. The charge pump includes a first current source, a second current source, and a first switch coupled between the first current source and the second current source. The filter is coupled to the charge pump between the first switch and the second current source. The second switch is coupled to the charge pump between the first current source and the first switch. The buffer is coupled between the filter and the second switch, with the buffer comprising a voltage buffer.

A successive-approximation register (SAR) analog-to-digital converter (ADC) circuit includes a comparator circuit and a plurality of latch circuits. The comparator circuit is configured to compare an analog signal with a plurality of reference levels. The latch circuits, coupled to the comparator circuit and connected in series, are triggered sequentially in response to a plurality of trigger signals, respectively, to store a comparator output of the comparator circuit and accordingly generate a digital signal. A first latch circuit and a second latch circuit of the latch circuits are triggered in response to a first trigger signal and a second trigger signal of the trigger signals, respectively. The first latch circuit is configured to generate the second trigger signal according to the comparator output stored in the first latch circuit.

The present invention relates to a frequency modulation method based on a phase-locked loop capable of performing fast modulation independent of bandwidth.

A frequency modulation system based on a phase-locked loop capable of performing fast modulation independent of bandwidth according to the present invention includes a loop filter including a proportional path and an integral path to determine a bandwidth of a phase-locked loop, a voltage-controlled oscillator configured to adjust a frequency according to an output of the loop filter, and a slope alternator configured to alternate an input current of the loop filter, wherein the slope alternator is located in the integral path of the loop filter to generate an offset current at a moment of change from a modulation rise to a modulation fall.

A phase-locked loop (PLL) circuit generates an analog signal in phase-lock with a reference signal at a reference frequency. The PLL circuit includes a charge pump circuit, a loop filter circuit, a feedback divider, and a voltage controlled oscillator (VCO). The charge pump circuit charges a sample capacitor of the loop filter circuit to a sample voltage based on a phase difference between the generated analog signal and the reference signal. The loop filter circuit stores the sample voltage as a proportional control voltage in a hold capacitor to reduce or avoid ripple in the control voltage that causes jitter in the analog signal. The loop filter circuit also provides the sample voltage to an integral component circuit comprising a comparator and digital accumulator producing an integral control. The VCO generates the analog signal at a frequency based on the proportional control voltage and the integral control voltage.