Abstract: A low power crystal oscillator is provided. The crystal oscillator includes a gain stage circuit having a first gain stage input coupled at a first oscillator terminal and configured to receive a first oscillator signal of a crystal. A first bias circuit is configured to generate a first bias voltage based on the first oscillator signal. A reference circuit is configured to generate a reference current based on the first bias voltage. A comparator circuit is configured to generate a clock signal based on the first oscillator signal and the first bias voltage. The comparator circuit includes a second bias circuit configured to generate a second bias voltage. The gain stage circuit includes a second gain stage input coupled to receive the second bias voltage.

Abstract: A digital phase-locked loop (PLL) includes a time-to-digital converter (TDC) and a digitally controlled oscillator (DCO). The DCO generates a PLL clock signal and various sampling clock signals that are mesochronous. The TDC samples a phase difference between a reference clock signal and a frequency-divided version of the PLL clock signal based on the sampling clock signals and various enable signals. The enable signals are generated based on a calibration of the digital PLL. Each enable signal is associated with a sampling clock signal and indicates whether the associated sampling clock signal is to be utilized for sampling the phase difference. Further, the TDC generates control data indicative of the sampled phase difference. The DCO generates the PLL clock signal and the sampling clock signals based on the control data until the digital PLL is in a phase-locked state.

Abstract: A calibration system of a digital phase locked loop (DPLL) includes a calibration circuit and a digitally controlled oscillator (DCO). The calibration circuit is configured to receive an input signal and a feedback signal, and generate a digital signal, based on a frequency of the input signal, a frequency of the feedback signal, and an input bias code. The DCO is configured to receive the input bias code and the digital signal, and generate a bias signal based on the input bias code. The DCO is further configured to generate an analog signal based on the bias signal and the digital signal, and generate the feedback signal such that the frequency of the feedback signal is based on an amplitude of the analog signal.

Abstract: A charge pump includes a charge pump core circuit, a replica bias circuit, and a differential amplifier. The charge pump core circuit includes current source and sink circuits for charging and discharging an output node of the charge pump core circuit. The current source and current sink circuits are user programmable using bit signals to adjust a bandwidth and a phase margin of a phase-locked loop (PLL) that includes the charge pump. An impedance of the replica bias circuit varies based on the bit signals. The differential amplifier and the replica bias circuit form a feedback loop that reduces current mismatch between the current source and sink circuits.

Abstract: A phase-locked loop (PLL) for generating an oscillating signal includes a frequency bounding circuit. When a frequency of the oscillating signal is greater than a first threshold value, which is greater than a maximum normal operational frequency of the PLL, the frequency bounding circuit forces a charge pump to discharge a loop filter until the oscillating signal frequency is less than a second threshold value that is within the normal operational frequency range of the PLL. When the frequency of the oscillating signal is less than a third threshold value, which is less than a minimum normal operational frequency of the PLL, the frequency bounding circuit forces the charge pump to charge the loop filter until the oscillating signal frequency is greater than a fourth threshold value that is within the normal operational frequency range of the PLL.

Abstract: A clock generator includes a diagnostic circuit that includes first and second muxes, first and second comparators, a logic gate, and a counter. The first mux receives first and second voltage signals and outputs a first intermediate signal based on a control signal. The second mux receives third and fourth voltage signals and outputs a second intermediate signal based on the control signal. The first and second comparators compare the intermediate signals with a first signal that is indicative of a DC value of the clock signal for generating first and second comparison signals. The logic gate receives the first and second intermediate signals and generates a control signal. The counter receives the clock signal and the control signal and generates a clock ready signal that is indicative of stability and quality of the clock signal.

Abstract: A buffer circuit includes an inverter and a level-shifter. The inverter receives a first oscillating signal at a first voltage level and generates an inverted version of the first oscillating signal at a second voltage level. The level-shifter receives a second oscillating signal at a third voltage level, which has a phase difference from the first oscillating signal, and the inverted first oscillating signal, and generates a buffer output signal at a fourth voltage level.

Abstract: A phase locked loop (PLL) system generates an oscillator signal by providing a fixed control voltage to a programmable voltage to current converter having switch selection inputs and a variable current output. Logic values are provided to the switch selection inputs to adjust a control current at the variable current output and a frequency of the oscillator signal is adjusted based on the control current. The logic values are fixed when a first condition is reached, which is based on the frequency of the oscillator signal, a division factor, and an input reference signal frequency. The fixed control voltage provided to the programmable voltage to current converter is then replaced with a charge pump control voltage based on an error signal. The error signal is based on a comparison of the input reference signal frequency and a fraction of the oscillating frequency.

Abstract: An oscillator includes an amplifier and a piezoelectric crystal coupled across a portion of the amplifier. A low pass filter (LPF) passes the common-mode voltage component of the crystal output signal. An auxiliary bias circuit uses a shared LPF component to charge a crystal load capacitor during start-up of the oscillator, and to provide a DC bias operating point to the oscillator driver transistor. A buffer amplifier receives the common-mode voltage component on the non-inverting input. The buffer amplifier output is coupled to both the inverting input and the drain terminal of the oscillator driver transistor such that the gate and drain DC bias voltages of the oscillator driver transistor are substantially the same. An automatic loop control circuit receives the crystal output signal and the common-mode voltage signal, and generates a bias control signal to bias the amplifier and the auxiliary bias circuit.

Abstract: A capacitor charging circuit has input, output and control nodes, first and second series connected primary FETs, and first and second leakage current reduction FETs. All of the FETs have their gates coupled to the control node. The first primary FET is coupled between the input and output nodes, and the second primary FET is coupled between the output node and a leakage current reduction node. The first leakage current reduction FET is coupled between a supply line and the leakage current reduction node, and the second leakage current reduction FET is coupled between the leakage current reduction node and ground. When a control signal at the control node is low, the first primary FET and the first leakage current reduction FET are conductive, and the second primary FET and the second leakage current reduction FET are non-conductive, which eliminates sub-threshold leakage current flowing through the second primary FET.

Abstract: A relaxation oscillator for generating an output clock signal includes an RC circuit, a self-biased comparator stage, and a logic circuit. The RC circuit generates first and second comparator input signals that are provided to the self-biased comparator stage. The self-biased comparator stage includes first and second input stages and a voltage reference circuit. Each of the first and second input stages in conjunction with the voltage reference circuit forms a comparator, i.e., first and second comparators corresponding to the first and second input stages, respectively. The self-biased comparator stage generates first and second comparator output signals, based on the first and second comparator input signals. The first and second comparator output signals are provided to the logic circuit that generates the output clock signal.

Abstract: A relaxation oscillator for generating an output clock signal includes an RC circuit, a self-biased comparator stage, and a logic circuit. The RC circuit generates first and second comparator input signals that are provided to the self-biased comparator stage. The self-biased comparator stage includes first and second input stages and a voltage reference circuit. Each of the first and second input stages in conjunction with the voltage reference circuit forms a comparator, i.e., first and second comparators corresponding to the first and second input stages, respectively. The self-biased comparator stage generates first and second comparator output signals, based on the first and second comparator input signals. The first and second comparator output signals are provided to the logic circuit that generates the output clock signal.

Abstract: A capacitor charging circuit has input, output and control nodes, first and second series connected primary FETs, and first and second leakage current reduction FETs. All of the FETs have their gates coupled to the control node. The first primary FET is coupled between the input and output nodes, and the second primary FET is coupled between the output node and a leakage current reduction node. The first leakage current reduction FET is coupled between a supply line and the leakage current reduction node, and the second leakage current reduction FET is coupled between the leakage current reduction node and ground. When a control signal at the control node is low, the first primary FET and the first leakage current reduction FET are conductive, and the second primary FET and the second leakage current reduction FET are non-conductive, which eliminates sub-threshold leakage current flowing through the second primary FET.

Abstract: A relaxation oscillator for generating an output clock signal includes a RC circuit, a bias generation stage, first and second comparator stages, and a logic circuit. The RC circuit generates first and second comparator input signals that are transmitted to the first and second comparator stages. The bias generation stage generates first and second bias voltages that are provided to each of the first and second comparator stages. The first and second comparator stages generate first and second comparator output signals, respectively, based on the first and second comparator input signals and the first and second bias voltages. The first and second comparator output signals are provided to the logic circuit that generates the output clock signal.

Abstract: A relaxation oscillator for generating an output clock signal includes a RC circuit, a bias generation stage, first and second comparator stages, and a logic circuit. The RC circuit generates first and second comparator input signals that are transmitted to the first and second comparator stages. The bias generation stage generates first and second bias voltages that are provided to each of the first and second comparator stages. The first and second comparator stages generate first and second comparator output signals, respectively, based on the first and second comparator input signals and the first and second bias voltages. The first and second comparator output signals are provided to the logic circuit that generates the output clock signal.

Abstract: A phase to digital converter for a digital PLL (Phase Locked Loop) provides an output in the same or single reference clock period for which it is digitizing the phase error information. The phase to digital converter operates on a positive edge of the reference clock and a digital filter operates on the negative edge of the reference clock so the phase correction performed by the PLL occurs in the same reference clock cycle in which the phase to digital converter is digitizing the phase error information.