Abstract: A technique and corresponding circuitry are presented for a process independent, self-calibrating relaxation based clock source. The technique and circuitry presented here can reduce the time and cost needed for calibration significantly. The relaxation based clock source produces a clock signal whose frequency is dependent upon a trim value. Starting from an initial trim value, the clock signal is generated, its frequency is compared with a reference clock frequency value, and the trim value is correspondingly adjusted up or down a bit at a time. After this process has continued for a while, min-max logic is used to determine the maximum and minimum trim values and, based on these, the final trim value for the clock is set. This calibration process can also be used to extract whether, and by how much, the implementation on silicon of a particular chip lies in the fast or slow process corners.

Abstract: Described embodiments provide a method of calibrating, by a calibration engine, a phase-locked loop (PLL) having one or more adjustable oscillators. The method includes entering a calibration mode of the PLL. The PLL is set to an initial state, thereby selecting one of the adjustable oscillators for calibration, an initial threshold window, and an initial tuning band of the selected adjustable oscillator. If the control signal of the selected adjustable oscillator is not within the initial threshold window, the calibration engine iteratively adjusts at least one of: (i) the selected tuning band of the selected adjustable oscillator, (ii) the selected adjustable oscillator, and (iii) the selected threshold window until the control signal of the selected adjustable oscillator is within the adjusted threshold window. If the control signal is within the threshold window, the one or more calibration settings of the PLL are stored and used to set the PLL operation.

Abstract: A method and a terminal for acquiring a frequency difference are disclosed. The method includes acquiring a difference T1 between clock timing before dormancy and clock timing of a base station, recording a dormancy period T between dormancy start and dormancy end, acquiring a difference T2 between clock timing after dormancy and clock timing of the base station, and computing a frequency difference between a low speed clock and a base station clock according to normalization frequencies, T1, T, and T2.

Abstract: A clock system includes a digital phase/frequency detector (DPFD), a buffer, a digitally-controlled oscillator (DCO) including a sigma-delta modulator (SDM), an adder, a first frequency divider. The DPFD may have a first input for a reference input clock and a second input for a feedback signal, and outputting a difference signal representing a phase and/or frequency difference between the reference input clock and the feedback signal. The first frequency divider may have an input for a clock signal and a control input coupled to the adder. The system clock also may include a phase-locked loop (PLL) including a phase/frequency detector that has a first input coupled to the output of the DCO and a second input that is phase-locked to the first input, and a second frequency divider coupled from the second input of the PLL to the second input of the DPFD.

Abstract: In one embodiment, the present invention includes a method of correcting the frequency of a crystal oscillator. The method includes establishing an operating baseline for the crystal oscillator using a frequency reference, storing information in memory, and adjusting the frequency according to the information. The information corresponds to the operating baseline. Adjusting the frequency occurs in response to a power-on event and the absence of the frequency reference.

Abstract: A phase locked loop (PLL) which has a desired frequency characteristic even though a manufacturing process of a semiconductor integrated circuit has fluctuations. The semiconductor integrated circuit includes the PLL and a control unit. The PLL has a phase frequency detector, a loop filter, a voltage controlled oscillator (VCO) and a divider. The VCO comprises a voltage-current converter (VIC) and a ring oscillator. In response to a control voltage, the VIC generates a control current for setting each operating current of the ring oscillator. The control unit switches the PLL to a calibration operating period of its open loop and a normal operating period of its closed loop.

Abstract: A method of detection of the presence of a contactless communication element by a terminal emitting an electromagnetic field, in which an oscillating circuit of the terminal is excited at a frequency which is made variable between two values surrounding a nominal tuning frequency of the oscillating circuit; a signal representative of the load of the oscillating circuit being interpreted to detect that a reference voltage has not been exceeded, which indicates the presence of an element in the field. A presence-detection circuit and a corresponding terminal.

Abstract: An oscillation signal with a selectable frequency is generated with a phase locked loop (10, 12, 14). The oscillator (10) of the loop receives a feedback signal, to which an offset is added in order to reduce transient effects when a frequency modification is made. A first and second offset control value are used to control the offset successively. The first offset control value is controlled by a combination of the frequency settings before and after the modification. The second offset control value is controlled by the frequency settings after the modification. The first and second offset control values are used to control an offset of applying to a frequency control signal of an oscillator (10) of the phase locked loop (10, 12, 14). The offset controlled by the first control offset value is applied during a predetermined time interval before the offset controlled by the second control offset value is applied.

Abstract: A clock system includes a digital phase/frequency detector (DPFD), a buffer, a digitally-controlled oscillator (DCO) including a sigma-delta modulator (SDM), an adder, a first frequency divider. The DPFD may have a first input for a reference input clock, a second input for a feedback signal, the DPFD generating an output representing a difference between the reference input clock and the feedback signal. The buffer may be coupled to the DPFD for storing the difference signal over time. The SDM may have a control input coupled to the buffer. The adder may have inputs coupled to the SDM and a source of an integer control word. The first frequency divider may have an input for receiving an external clock signal and a control input coupled to the adder, the DCO generating an output clock signal having an average frequency representing a frequency of the external clock signal divided by (N+F/M).

Abstract: In a PLL circuit, a threshold discriminator generates a control signal indicating a relative level of a control voltage. A controller outputs a controlling value based on the control signal. If the control signal indicates a high level when the controlling value specifies a control voltage-to-oscillation frequency correspondence relation whose upper and lower limits of oscillation frequency are highest, and if the control signal indicates a low level when the controlling value specifies a correspondence relation whose upper and lower limits of oscillation frequency are lowest, the controller outputs a predetermined controlling value. An oscillator has the correspondence relations set therein such that the correspondence relations have respective different upper and lower limits of oscillation frequency and are correlated with the respective controlling values.

Abstract: A VCO in a phase-locked loop (PLL) is arranged to receive low-pass data via a first input and high-pass data at a second input. The first input is coupled to a first set of varactors in the VCO. The second input is coupled to a second set of varactors in the VCO. The controller sets the input voltage at the first input and directs a charge pump to operate in a tri-state mode that opens the feedback loop of the PLL. The controller applies different voltages via the second input and measures the change in output frequency. A present gain of the VCO is determined from the ratio of the change in frequency and the change in voltage at the second input.

Abstract: A phase locked loop (PLL) which has a desired frequency characteristic even though a manufacturing process of a semiconductor integrated circuit has fluctuations. The semiconductor integrated circuit includes the PLL and a control unit. The PLL has a phase frequency detector, a loop filter, a voltage controlled oscillator (VCO) and a divider. The VCO comprises a voltage-current converter (VIC) and a ring oscillator. In response to a control voltage, the VIC generates a control current for setting each operating current of the ring oscillator. The control unit switches the PLL to a calibration operating period of its open loop and a normal operating period of its closed loop.

Abstract: A technique and corresponding circuitry are presented for a process independent, self-calibrating relaxation based clock source. The technique and circuitry presented here can reduce the time and cost needed for calibration significantly. The relaxation based clock source produces a clock signal whose frequency is dependent upon a trim value. Starting from an initial trim value, the clock signal is generated, its frequency is compared with a reference clock frequency value, and the trim value is correspondingly adjusted up or down a bit at a time. After this process has continued for a while, min-max logic is used to determine the maximum and minimum trim values and, based on these, the final trim value for the clock is set. This calibration process can also be used to extract whether, and by how much, the implementation on silicon of a particular chip lies in the fast or slow process corners.

Abstract: An integrated circuit radio transceiver and method therefor includes capacitive loop filter with selectable capacitive elements that are operable to adjust a signal level provided to a voltage controlled oscillator to control a frequency of an output signal of the oscillator. A plurality of switches are controlled by logic to define a discharge mode, a charge mode and charge sharing mode in which a plurality of capacitive elements share charge while generating the input voltage to the oscillator.

Abstract: A phase locked loop can reduce a locking time, thereby efficiently reducing power in a locking operation. The phase locked loop includes a phase detector, a control voltage generator, a voltage controlled oscillator and a start-up driver. The phase detector detects a phase difference between a reference clock and a feedback clock to generate a detection signal corresponding to the detected phase difference. The control voltage generator generates a control voltage having a voltage level corresponding to the detection signal. The voltage controlled oscillator generates an internal clock having a frequency corresponding to a voltage level of the control voltage. The start-up driver drives a control voltage terminal to a predefined start-up level in response to a start-up level multiplex signal corresponding to a frequency of the reference clock prior to activation of the voltage controlled oscillator.

Abstract: To provide a highly stable oscillation frequency control circuit wherein the frequency thereof is corrected, an adequate range of the input levels of external reference signals is determined in accordance with temperature characteristics in detecting the external reference signal, and the control voltage to a VCO is controlled within and outside the adequate range. An oscillation frequency control circuit includes a selection switch that connects the phase comparator to the loop filter in an external reference synchronization mode and that connects the fixed voltage supplying circuit to the loop filter in a fixed voltage mode, and a CPU that switches the selection switch to the external reference synchronization mode or to the fixed voltage mode based on whether the detected voltage of an external reference signal level is within or outside of the adequate range.

Abstract: A synchronizing apparatus, which controls, by a PLL circuit, a sampling clock to be used to sample input data and synchronizes a phase of the sampling clock with a target phase that is desirable for sampling the input data, includes: phase error detection means for detecting a phase error from sampling data and the sampling clock, the sampling data being sampled from the input data at timing of the sampling clock; frequency error detection means for detecting, based on a differential coefficient obtained as a result of detecting the phase error, a frequency error; and frequency correction means for correcting a frequency of the sampling clock such that the detected frequency error becomes close to zero by adding a frequency correction value to an integral term of a loop filter of the PLL circuit, the frequency correction value being calculated based on the frequency error.

Abstract: A two-point phase modulator and a method of calibrating conversion gain of the same are provided. The two-point phase modulator locks an output frequency signal by charging and pumping charge in a phase-locked loop (PLL) circuit at the beginning of operation, opens a loop of the PLL circuit for a period of time, and applies a step signal, thus calibrating conversion gain of a modulation signal that controls the output frequency signal. Thus, the conversion gain may be accurately calibrated by the calibration operation at one time.

Abstract: A method of calibrating oscillators is disclosed that includes searching, in an array storing an operational characteristic of the oscillator, for an index value that is associated with an output of the oscillator; determining that the output is within a predetermined accuracy as compared to a desired output; and generating the output based the index value. An apparatus for performing the method is also disclosed herein.

Abstract: A phase-locked loop circuit having a dual-reference input and a phase detector. The dual-reference input is configured to accept both a rising edge of an input clock having a first phase and a falling edge of the input clock having a second phase. The phase detector is coupled to the dual-reference input and is configured to produce a center phase signal based upon and centered in phase between the first and second phases. The phase detector is further configured with a feedback loop to adjust any tracking error and provide a tracking output signal. The phase detector system maintains both a high tracking bandwidth and a bounded jitter amplification based as a result of the dual reference signal. The high tracking bandwidth and the bounded jitter amplification are independent of an applied loop gain.

Abstract: An object is to provide a PLL having a wide operating range. Another object is to provide a semiconductor device or a wireless tag which has a wide operating range in a communication distance or temperature by incorporating such a PLL. The semiconductor device or the wireless tag includes a first divider circuit; a second divider circuit; a phase comparator circuit to which an output of the first divider circuit and an output of the second divider circuit are provided; a loop filter to which an output of the phase comparator circuit is supplied and in which a time constant is switched in accordance with an inputted signal; and a voltage controlled oscillator circuit to which an output of the loop filter is supplied and which supplies an output to the second divider circuit.

Abstract: The invention relates to a method for carrying out a frequency change whilst retaining the phase relationship between several devices, in particular, network analyzers. Each device has at least one signal generator for stimulating an object for measurement and at least one local oscillator, connected to at least one mixer, for receiving a measuring signal obtained from the object for measurement by the superposition principle. On changing frequency, in a first step, only the frequency of the local oscillators of all devices is changed and the frequency of the signal generators of all devices remains unchanged. In a second step, only the frequency of at least one signal generator is changed and the frequency of the local oscillators of all devices remains unchanged.

Abstract: Embodiments of the invention include a method for use in a device having a local oscillator. The method includes performing, for the local oscillator that is disciplined by an external reference signal, while locked to the external reference signal, training at least two mathematical models of the oscillator to determine a predicted correction signal for each mathematical model based at least in part on a correction signal that is a function of the external reference signal and which is used to discipline drift in the oscillator. The method also includes selecting a mathematical model of the at least two mathematical models that results in a smallest time error when disciplining the oscillator to use when the external reference signal is unavailable and an alternative correction signal is to be used to discipline drift in the oscillator.

Abstract: A method for calibrating a phase locked loop begins by determining a gain offset of a voltage controlled oscillator of the phase locked loop. The processing then continues by adjusting current of a charge pump of the phase locked loop based on the gain offset.

Abstract: There is provided a small-size, low-power-consumption intermittent operation circuit capable of obtaining an output waveform having a rapid rise and fall. The intermittent operation circuit includes an active circuit (106), a first control signal generation circuit (101) for generating a first control signal (S1) for controlling the operation start and the operation end of the active circuit (106), a second control signal generation circuit (102) for generating a second control signal (S2) causing the active circuit (106) to perform ringing vibration and controlling the frequency and the amplitude value of the ringing vibration, and a timing adjusting circuit (103) for adjusting the input timing of the first and the second control signal (S1, S2) into the active circuit (106) so that the ringing vibration and the safety vibration are outputted continuously from the active circuit (106).

Abstract: An integrated circuit radio transceiver and method therefor includes capacitive loop filter with selectable capacitive elements that are operable to adjust a signal level provided to a voltage controlled oscillator to control a frequency of an output signal of the oscillator. A plurality of switches are controlled by logic to define a discharge mode, a charge mode and charge sharing mode in which a plurality of capacitive elements share charge while generating the input voltage to the oscillator.

Abstract: The disclosure provides systems and methods for programmable fixed frequency digitally controlled oscillators for multirate low jitter frequency synthesis. The present invention utilizes a digital control element, such as a complex programmable logic device (CPLD) or field programmable gate array (FPGA), to monitor the frequency offset of a DCO with respect to one or more timing module (TM) references. The frequency offset is measured by aligning the phase of a DCO feedback divider to the phase of a reference divider, and then counting the number of pulses in the DCO between the falling edges of the feedback to determine a frequency error. Falling edge detection is used to determine a sign of the error. The digital control element then calculates a frequency correction based on a linear scaling factor to send a new control word to the DCO to reduce the frequency error.

Abstract: In a circuit having a runaway detector coupled to a phase-locked loop (PLL), the PLL may include a loop filter to receive a control voltage within the PLL and provide a filtered control voltage and a voltage-controlled oscillator to receive the filtered control voltage and provide an output clock signal. The runaway detector may provide a control signal for adjusting the filtered control voltage in response to a predetermined PLL condition. The runaway detector may include a comparator to receive a first and second input voltages, where the second input voltage is based on the output clock signal. When the predetermined PLL condition exists, the runaway detector may be active to adjust the filtered control voltage, thereby enabling the PLL to return to a lock condition.

Abstract: A method and circuit for providing coherent phase noise including a clock receiver to receive a clock signal generated external to the circuit and a local clock source arranged on the circuit. The circuit further includes a selector to select an output of one of the clock receiver and the local clock source and a wireless transceiver responsive to an output of the selector.

Abstract: Provided is a current control circuit. A current control circuit may include a clock sensing unit configured to generate a control signal according to one or more frequencies based on a plurality of clock signals, and a current scaling unit configured to scale a bias current according to the control signal. The current control circuit according to example embodiments may dynamically control a bias current according to one or more frequencies based on a plurality of clock signals so that power consumption of an analog-to-digital converter (ADC) and the semiconductor device including the ADC, which require various operating frequencies, may be improved.

Abstract: A novel mechanism that is operative to observe and compare the differentiated phase of the reference and variable PLL loop signals using a frequency detector. The resultant phase differentiated error is then accumulated to yield the phase error. The operation of the loop with the frequency detector is mathematically equivalent to that of the phase detector. A frequency error accumulator is used to generate the integral of the frequency error. The frequency error accumulator also enables stopping the accumulation of the frequency upon detection of a sufficiently large perturbation, effectively freezing the operation of the loop as subsequent frequency error updates are not accumulated. Upon removal of the phase freeze event, accumulation of the frequency error and consequently normal loop operation resumes.

Abstract: An apparatus for the phase synchronization of several devices, wherein one device is the master device and the other devices are slave devices, with a phase synchronization unit for every device, each of which has: a first controlled oscillator for producing a master reference signal, a first phase detector which, in order to control the first oscillator, compares the phase of a first comparison signal derived from the master reference signal with the phase of a second comparison signal derived from an auxiliary reference signal if the device is itself the master device and a second phase detector which, in order to control the first oscillator, compares the phase of a third comparison signal derived from the master reference signal with the phase of a reference signal coming from the phase synchronization unit of the master device if the device is not itself the master device but a slave device.

Abstract: A PLL circuit for two point modulation includes a first loop filter, a second loop filter, a plurality of switching devices, and a calibration module. The first loop filter filters an output voltage of a charge pump during a gain calibration operation. The second loop filter filters the output voltage of the charge pump during a normal operation. The first loop filter has a bandwidth wider than that of the second loop filter to perform a fast calibration by reducing a lock time. The operation of the first loop filter, the operation of the second loop filter, and the opening of the first loop filter are determined by the switching operations of the switching devices. The calibration module adjusts a gain of analog modulation data based on a frequency error accumulated in the first loop filter after the first loop filter is open during the gain calibration operation.

Abstract: Provided is a PLL apparatus outputting a frequency signal from a voltage-controlled oscillation unit in synchronization with an external reference frequency signal, in which the fluctuation of the frequency is reduced even when the external reference signal has a trouble For solving the problem, as a result of monitoring the signal level of the external reference frequency signal, when its signal level falls within a set range, data regarding a phase difference created by a phase difference data creating means is used for the PLL control, but when the signal level does not fall within the set range, it is recognized that the supply of the signal has been stopped or the supplied signal has abnormality and the data regarding the phase difference stored in a storage unit, for example, the stored latest data or the pre-created data is used instead for the PLL control.

Abstract: To provide a phase locked loop circuit that is capable of performing an automatic adjustment that satisfies a desired characteristic not depending on a process variation and an environmental variation. The phase locked loop circuit has a phase frequency comparator, a charge pump, a loop filter, a frequency divider, a selector, and a voltage controlled oscillator. The frequency divider inputs an output signal and a reference signal, divides the output signal, and outputs a feedback signal, and also outputs a select signal, a trimming signal, and a limit signal from the output signal. The voltage controlled oscillator inputs the control voltage, the base voltage, the trimming signal, and the limit signal, changes the output signal frequency according to the control voltage so as to limit the upper limit frequency of the output signal.

Abstract: A phase locked loop has a digitally controlled oscillator (DCO) for generating a DCO output signal (fOSC), a clock divider coupled to the DCO and receiving the DCO output signal and outputting a feedback clock signal (fN), and a phase frequency detector (PFD) coupled to the DCO and controlling the DCO by a DCO control signal (dCNTL).

Abstract: A system and method for generating a highly stable holdover clock utilizing an integrated circuit and an external OCXO is presented. The integrated circuit comprises an input reference clock receiver, a phase and frequency detector that generates an error signal between the input reference clock signal and a feedback clock signal, a data storage block that stores model parameters to predict frequency variations of the OCXO, an adaptive filtering module that includes a digital loop filter and algorithms for updating the model parameters and predicting frequency variations based on the model, a switch that enables the system to operate in normal or holdover mode, a digitally controlled oscillator, and a feedback divider.

Abstract: A phase detecting module includes a phase detecting unit, a comparator and a counter. The phase detecting unit is arranged to compare a first input signal and a second input signal to generate a phase detecting result. The comparator is arranged to compare the phase detecting result and a predetermined voltage to generate a comparing result. The counter is arranged to count one of the first input signal and the second input signal to generate a counting value. The phase detecting result and the counting value are reset if the counting value reaches a predetermined value, and the comparing result is outputted to a target device from the comparator if the counting value reaches a predetermined value.

Abstract: A lock loop circuit (216) includes a precharge circuit (304), an oscillator circuit (306), and a calibration circuit (309). The calibration circuit includes at least one register (362). The precharge circuit provides a precharge signal (347). The oscillator circuit provides an output frequency signal (228) in response to a steering signal (334) that is based on the precharge signal. The calibration circuit, prior to the lock loop circuit entering a disabled mode of operation, determines a calibration value (368) for the precharge circuit based on the precharge signal and the steering signal. The calibration circuit stores the calibration value as a digital calibration value (370) in the register.

Abstract: A voltage controlled oscillator 8 is configured to include a plurality of variable delay circuits 30 that are connected to one another so as to form a ring. Output fixing units 31 each of which fixes, when the voltage controlled oscillator 8 stops operating, the output of a corresponding one of the variable delay circuits 30 are provided. As a result, even if the voltage controlled oscillator 8 that operates by following the frequency of an input clock has changed into an operation stop state, because the output fixing units 31 fix the outputs of the variable delay circuits 30, the output of the voltage controlled oscillator 8 is prevented from being in an inconstant state. Thus, it is possible to ensure that the voltage controlled oscillator 8 oscillates properly when the voltage controlled oscillator 8 resumes or starts its operation.

Abstract: Systems and methods for enabling the determination of voltage controlled oscillator (VCO) linearity, duty cycle determination and duty cycle correction in phase locked loop circuits (PLL's.) One embodiment comprises a method including the steps of determining the frequency response of a PLL's VCO as a function of duty cycle, applying a signal based on the VCO output to the VCO input, measuring the resulting frequency of the VCO output signal, determining the duty cycle corresponding to the measured frequency, and configuring a duty cycle correction unit correct the duty cycle of the VCO output signal to about 50%. Determining the frequency response of the VCO may include, for each of several different duty cycle values between 0% and 100%, applying the VCO input signal to the VCO and determining the corresponding frequency of the VCO output signal. This may also be done for duty cycles of 0% and 100%.

Abstract: A clock generator includes a ring oscillator for outputting a basic signal, a divide-by-N frequency divider for dividing the basic signal by a division ratio N to generate a clock signal having a target frequency, a divide-by-two frequency divider for dividing the clock signal by two when an enable signal is on, a counter for counting the number of pulses of the basic signal for a predetermined period of time, a calculator for calculating the division ratio N, and a comparator for comparing a count value of the counter with a threshold value. When the count value of the counter is less than the threshold value, the comparator turns on the enable signal. Thus, when a temperature of the ring oscillator increases, the frequency of the clock signal is reduced to half the target frequency.

Abstract: An oscillation device includes a reference oscillation unit for generating an oscillating signal of a specific frequency; a voltage-controlled oscillation unit for generating a output oscillation signal whose frequency is dependent on a control voltage; a phase comparing unit for detecting a phase difference based on the oscillating signal and the output oscillation signal; a digital value storage unit for storing therein a phase difference signal corresponding to the phase difference as a digital value; a sample holding unit for intermittently renewing and maintaining a hold signal in accordance with the digital value; and a control unit. The control unit controls the reference oscillation unit, the phase comparing unit and the digital value storage unit to be started or stopped, and also switches the control voltage to the phase difference signal or to the hold signal.

Abstract: Aspects of a method and system for using a frequency locked loop LOGEN in oscillator systems may include generating an oscillating signal via one or more circuits comprising a feedback loop. The generation may be controlled by enabling or disabling the feedback loop, based on the generated oscillating signal. The one or more circuits may comprise a frequency-locked loop (FLL) that may enable the generation of the oscillating signal. The frequency-locked loop may comprise a voltage-controlled oscillator. The feedback loop may be disabled when an estimated frequency difference between a reference signal and a feedback signal may be less than or equal to a specified threshold. The feedback loop may be enabled when an estimated frequency difference between a reference signal and a feedback signal may be greater than a particular threshold.

Abstract: The present invention relates to a phase locked loop arrangement having an oscillator circuit (240) controlled in response to an output signal of a phase or frequency detection circuit (210), wherein change control means (130) are provided for generating a blocking signal in response to the outputs of a first timer means (110) to which a predetermined threshold frequency is supplied and a second timer means (112) to which an output frequency of the oscillator circuit (240) is supplied. Based on the blocking signal, blocking means (260) suppress supply of the output signal to said oscillator circuit (240). Thereby, the output frequency of the PLL arrangement can be prevented from changing beyond the frequency threshold, while only one PLL circuit is required.

Abstract: A method for calibrating a phase locked loop begins by determining a gain offset of a voltage controlled oscillator of the phase locked loop. The processing then continues by adjusting current of a charge pump of the phase locked loop based on the gain offset.

Abstract: A phase lock control system is presented for controlling a voltage controlled oscillator. The system includes a voltage controlled oscillator that produces a frequency signal exhibiting an output frequency that varies dependent upon the value of a control voltage applied thereto. A frequency deviation determining system employs a counter intermittently triggered ON for a fixed time by successive timing pulses received from a reference source and a comparator that determines any frequency deviation of the output frequency relative to a preset frequency. An error filter monitors the comparator for any frequency deviation for a plurality of samples of the frequency deviation determinations. A controller varies the control voltage to vary the output frequency in a direction to eliminate any frequency deviation.

Abstract: A PLL circuit has (i) a counter which divides a frequency of a VCO output whose frequency has been divided by a frequency divider and (ii) a memory which stores plural patterns of set cycles of the counter. The memory reads out one of the set cycles designated by a selection signal inputted through a serial bus (SB) from an outside of the PLL circuit. The set cycle, read out from the memory, which has a large amount of data, is inputted through a parallel bus (PB) into the counter, so that it hardly takes time to set a cycle for the counter. Further, even when the number of bits of the counter increases, the setting time is not lengthened.

Abstract: To provide a phase locked loop circuit that is capable of performing an automatic adjustment that satisfies a desired characteristic not depending on a process variation and an environmental variation. The phase locked loop circuit has a phase frequency comparator, a charge pump, a loop filter, a frequency divider, a selector, and a voltage controlled oscillator. The frequency divider inputs an output signal and a reference signal, divides the output signal, and outputs a feedback signal, and also outputs a select signal, a trimming signal, and a limit signal from the output signal. The voltage controlled oscillator inputs the control voltage, the base voltage, the trimming signal, and the limit signal, changes the output signal frequency according to the control voltage so as to limit the upper limit frequency of the output signal.

Abstract: To calibrate an oscillator for microcontroller chip operation, an RC circuit is coupled to the microcontroller circuitry and a voltage signal is applied to the capacitor for changing the voltage across the capacitor. The voltage value across the capacitor is measured and compared to an expected voltage value. Adjustments to the frequency of the clock signal generated by the oscillator are made in response to the comparison.