Abstract: A low-speed general-purpose inspection apparatus is used to automatically adjust a variable delay circuit and compensate for a delay variation in order to enable an inspection and to achieve a reduction in cost and an improvement in an inspection quality.

Abstract: An apparatus for generating an output clock is disclosed. The apparatus comprises: N variable offset clock circuits for receiving N input clocks and for generating N intermediate clocks having N phase offsets controlled by N intermediate signals, respectively, where N>1; a clock multiplexer for selecting one of the N intermediate clocks as the output clock according to a finite-state signal having N possible states; and a finite-state-machine for receiving a control signal and the N intermediate clocks and for generating the finite-state signal and the N intermediate signals.

Abstract: A circuit apparatus and method for generating multiphase clocks in a delay lock loop (DLL) at sub-picosecond granularity. The circuit and method of the invention involves locking a number of cycles M in an N stage DLL, e.g., M cycles, where M is an prime number, which results in clock edges in each cycle that are not located at the same phase locations in each of the M cycles. Any of the phase locations from any of the cycles can be used to generate a clock edge for all cycle in the system application. This requires a special technique to “lock” the DLL loop over a M cycle period instead of a one cycle period. The benefit is that it improves the clock placement granularity by a factor of M over the previous art.

Abstract: The present invention provides a delay apparatus for delaying an input signal by a predetermined delay amount, including: a plurality of delay units for respectively delaying the input signal by the predetermined delay amount, each delay unit having a plurality of delay cells for respectively delaying the input signal by a certain delay period; and a sub decoding unit for generating a plurality of sub control signals to each of the delay units according to a first control signal and a selecting signal, wherein only delay cell of all the delay units is outputted at a time according to the sub controls signals.

Abstract: A high speed passband phase modulation apparatus and method are provided. In the phase modulation apparatus, an RF phase shifter modulates a phase of a local signal that is generated in a VCO according to a digital input. The RF phase shifter is controlled by a phase-controlled loop so that a baseband phase shifter is phased locked to a modulation reference signal from the local signal and a reference clock signal according to the digital input. The phase-controlled loop phase-locks using the modulation reference signal so that the phase-modulated signal generated in the RF phase shifter has a phase value according to the digital input.

Abstract: A delay circuit includes: a current control circuit which has n (n is 1 or larger natural number) control pins and a first output line, and is capable of controlling current outputted from the first output line in response to n control signals inputted to the corresponding n control pins; a current mirror circuit connected with the first output line to produce current mirror current from the current and output the current mirror current from a second output line; a first active element having a gate pin and an input pin, the gate pin is connected with the second output line, and the input pin is connected with the first voltage line; a second active element having a gate pin and an input pin, the gate pin is connected with the first output line, and the input pin is connected with the second voltage line; and an inverter circuit having third and fourth active elements connected in series between an output pin of the first active element and an output pin of the second active element.

Abstract: A data output strobe signal generating circuit includes a duty cycle correcting unit that corrects the duty ratio of an input clock in response to a control signal to generate a corrected clock. A data output strobe signal generating unit receives the corrected clock and generates a data output strobe signal. A duty cycle control unit receives the data output strobe signal and outputs the control signal.

Abstract: There is provided a skew adjusting apparatus for adjusting a skew between a positive-side differential signal and a negative-side differential signal in differential signals inputted from an outside device via outside transmission lines, having a positive-side transmission line for propagating the positive-side differential signal inputted to an input end, a negative-side transmission line for propagating the negative-side differential signal inputted to an input end, a plurality of differential comparators connected with the positive-side and negative-side transmission paths so that a difference between wiring length from the input end of the positive-side transmission path and wiring length from the input end of the negative-side transmission path is different from each other and that take in the positive-side differential signal and the negative-side differential signal and a selecting section for selecting a signal taken in by the differential comparator by which a skew between the positive-side path from

Abstract: Systems and methods for transmitting a signal having a desired phase at the device are disclosed. The systems and methods further include determining a signal path length to a device over a transmission line and adding a delay to a signal to be transmitted over the transmission line. The determination is made in response to determining the path length to the device.

Abstract: A time-to-digital converter (TDC), a system-on-chip including a TDC, a method of phase detection for use in synthesizing a clock signal and a non-linearity corrector for a TDC. In one embodiment, the TDC includes a chain of delay elements configured to receive a clock signal and generate delayed clock signals. Each one of the delay elements includes: (1) a non-inverting buffer configured to delay the clock signal by about twice a delay of an inverter to provide a buffer-delayed clock signal and (2) a first transmission gate coupled to the non-inverting buffer and configured to delay the clock signal by about the delay of an inverter to provide a first gate-delayed clock signal.

Abstract: A digital high speed programmable delayed locked loop (DLL) includes a zero degree phase shift digital delay line, at least one intermediate phase shift digital delay line, a three hundred and sixty degree phase shift digital delay line, and a digital control module. The zero degree phase shift, intermediate phase shift, and 360 degree phase shift digital delay lines are operably coupled to produce, from a clock signal, zero phase shifted, intermediate phase shifted, and 360 phase shifted representations, respectively, of the clock signal. The digital control module is operably coupled to produce an intermediate control signal for the intermediate phase shift digital delay line and a 360 degree control signal for the 360 degree phase shift digital delay line based on a phase difference between the zero phase shifted representation of the clock signal and the three hundred and sixty degree phase shifted representation of the clock signal.

Abstract: A clock multiplier includes a phase-locked loop (PLL), a bias generator, a counter, a selection circuit, a flip-flop, a phase comparator, a delay controller and a variable delay circuit. The variable delay circuit, which is biased by a delay cell bias signal, delays a reference signal by a first delay time and by a second time that is longer than the first delay time, and generates a first feedback signal corresponding to the first delay time, and a second feedback signal corresponding to the second delay time. Therefore, a clock multiplier may reduce the size of a delay cell and may be designed to be insensitive to changes in environmental conditions, such as a process, a voltage, a temperature, and so on.

Abstract: This disclosure relates to a cell-placeable variable-frequency digitally controlled oscillator (DCO) that consumes approximately the same current in a fast process corner as in the case of a slow process corner. By modulating the effective channel length of transistors in inverters, a fast process DCO may be slowed down to a desired frequency at nearly the same current consumption as that of a slow process DCO.

Abstract: Disclosed herein is a VDL/DLL architecture in which the power supply to the VDL, VccVDL, is regulated at least as a function of the entry point of the input signal (ClkIn) into the VDL. Specifically, VccVDL is regulated to be higher when the delay through the VDL is relatively small (when the entry point is toward the right (or minimum delay) edge of the VDL) and is reduced when the delay is relatively high (when the entry point is toward the left (or maximum delay) edge of the VDL). This provides for graduated delays across the stages of the VDL, but without the need to design each stage separately. Other benefits include a VDL/DLL design operable over a wider range of frequencies, and a reduced number of stages, including a reduced number of buffer stages. Moreover, when the disclosed technique is used, buffer stages may be dispensed with altogether.

Abstract: A semiconductor memory device includes a first clock buffer for outputting a first internal clock signal in response to an inverted signal of the system clock signal and for correcting a duty cycle ratio of the first internal clock signal in response to a control signal; a second clock buffer for outputting a second internal clock signal in response to the system clock signal and for correcting a duty cycle ratio of the second internal clock signal in response to the control signal; an analog duty cycle correction circuit for outputting the control signal corresponding to the duty cycle ratio of the first and second internal clock signals; a mixing circuit for mixing the first and second internal clock signals and for outputting a third internal clock signal whose duty cycle is corrected; and a DLL circuit for outputting a delay-locked clock signal by using the third internal clock signal.

Abstract: A current mode logic (CML) delay cell with linear rail-to-rail tuning range and constant output swing. The CML delay cell can include a tuning voltage input on a first and second transistor, contributing to a CML delay cell load, and a bias voltage input on a third transistor, as a current source I0, and a compensation circuit having switching point optimized inverters having a first plurality of transistors having a transconductance ?pN and a second plurality of transistors having a transconductance ?nN, wherein respective ratios of ?nN/?pN determine an inverter switching point of respective switching point optimized inverters, the first and second plurality of transistors having gates coupled to the tuning voltage input of the CML delay cell, wherein the switching point optimized inverters are followed by weighted tail current sources M0N that supply additional currents to the current source I0 at a drain node of the third transistor.

Abstract: Apparatus for correcting clock skew in a circuit including at least one sequential circuit element and a clock generator operatively coupled to the sequential circuit element includes at least one programmable delay element connected in series with a data input and/or a clock input of the sequential circuit element. The programmable delay element has a delay associated therewith which is selectively controllable as a function of a control signal. The apparatus further includes at least one processor connected in a feedback configuration with the sequential circuit element. The processor is operative to receive a clock signal generated by the clock generator and an output signal of the sequential circuit element and to generate the control signal as a function of the clock signal and the output signal. The processor is further operative to control a timing of a data signal supplied to the data input of the sequential circuit element.

Abstract: A methodology is disclosed that enables the delay stages of an analog delay locked loop (DLL) or phase locked loop (PLL) to be programmed according to the operating condition, which may depend on the frequency of the input reference clock. The resulting optimized delay stages allow for a broad frequency range of operation, fast locking time over a wide range of input clock frequencies, and a lower current consumption at high clock frequencies. Better performance is achieved by allowing the number of analog delay stages active during a given operation to be flexibly set. The deactivation or turning off of unused delay stages conserves power at higher frequencies. The high frequency range of operation is increased by using a flexible number of delay stages for various input clock frequencies. Because of the rules governing abstracts, this abstract should not be used to construe the claims.

Abstract: The invention relates to electronic devices for generating synchronization signals, in particular to ultrahigh resolution synchronization signals whose temporal accuracy is less than a nanosecond. The inventive device operates not only with an internal clock but also with the external clock of a synchronizable device, thereby avoiding any temporal drift and uncertainty of the synchronization signals. The main element of the device is embodied in the form of a programmable digital component which operates with the external clock frequency and comprises programmable delay lines enabling to attain ultrahigh temporal resolutions. Said invention also relates to a system comprising several synchronization devices which are interconnected in such a way that the synchronization of different devices remains perfect. The invention makes it possible to control with high accuracy a quasi-unlimited number of devices.

Abstract: In a phase locked loop circuit, a phase comparator compares the phase of input clock and that of output clock, and provides a control signal as the comparison result. A charge pump circuit includes a clamp circuit, and based on the control signal, provides a control voltage of which lower limit is the reference voltage level. A voltage controlled oscillator receives the control voltage and a second control voltage from the outside and generates output clock having a frequency in accordance with the control voltages. Each delay stage of a delay section is configured with a plurality of delay units identical to that in the voltage controlled oscillator. The delay stage controls the delay time in response to the supply of the control voltage and the second control voltage.

Abstract: Some embodiments include a delay locked circuit having multiple paths. A first path measures a timing of a first clock signal during a measurement. A second path generates a second clock signal based on the first clock signal. The delay locked circuit periodically performs the measurement to adjust a timing relationship between the first and second clock signals. The time interval between one measurement and the next measurement is unequal to the cycle time of the first clock signal. Additional embodiments are disclosed.

Abstract: The present invention provides a delay apparatus for delaying an input signal by a predetermined delay amount, including: a plurality of delay units for respectively delaying the input signal by the predetermined delay amount, each delay unit having a plurality of delay cells for respectively delaying the input signal by a certain delay period; and a sub decoding unit for generating a plurality of sub control signals to each of the delay units according to a first control signal and a selecting signal, wherein only delay cell of all the delay units is outputted at a time according to the sub controls signals.

Abstract: Frequency multiplying delay-locked loop techniques are described in which a plurality of phase shifted signals are generated which have increased frequency relative to the incoming signal.

Abstract: A method and apparatus for pre-clocking have been disclosed.

Abstract: A delay-locked loop includes a phase detector, a delay line, and a filter unit. The phase detector compares the phase of the external clock signal with that of the feedback clock signal and outputs a phase difference as an error control signal. The delay line includes delay cells having various unit time delays. The number of delay cells is adjusted in response to a shift signal. The delay line receives the external clock signal and outputs an output clock signal. The filter unit generates the shift signal in response to the error control signal. In the delay-locked loop, the front delay cells, which compensate for a delay of an external clock signal having a high frequency, have short unit time delays. The rear delay cells, which compensate for a delay of the external clock signal having a low frequency, have long unit time delays.

Abstract: A delayed lock loop for preventing a stuck fail in a dead-zone includes a clock buffering block for generating a first and a second internal clock signals; a phase comparison block for delaying a feedback signal by a first predetermined value and for respectively comparing a phase of a delayed feedback signal and a phase of the feedback signal with a phase of the external clock signal; a clock selecting block for selecting one of the first and second internal clock signals based on one comparison result to thereby generate a selected internal clock signal; a stuck checking block for determining a delay value based on the other comparison result; a delay line block for delaying the selected internal clock signal by the delay value; and an output buffer for buffering an outputted signal from the delay line block to thereby generating a DLL clock signal.

Abstract: Embodiments of the present invention include an integrated circuit comprising an integrated transmission line, wherein the integrated transmission line is used as a timing reference for a feedback loop and wherein the feedback loop and the transmission line are integrated on a single integrated circuit. The feedback loop and transmission line may be used as a frequency generator or controlled delay, for example. In another embodiment, the present invention includes a timing loop with first and second commutating phase detectors.

Abstract: A tunable delay line is calibrated to maintain the delay of the delay line at a desired value or within a desired range of values. In some aspects a signal is passed through a delay line multiple times so that the cumulative delay of the signal through the delay line (e.g., as indicated by a count) may be calculated over a period of time. The count is compared with an expected count and, based on this comparison, the delay of the delay line is adjusted as necessary. In some aspects the signal may comprise a digital signal. In some aspects a delay through a delay line may be calculated based on analysis of amplitude changes in a signal caused by a phase shift imparted on the signal by the delay line. In some aspects a delay line is incorporated into a transmitted reference system to generate and/or process transmitted reference signals.

Abstract: Digital delay-locked loops (DLLs) and methods are provided for signal frequency multiplication. Analog delay elements of typical frequency-multiplying DLLs are replaced with digital and digitally-controlled elements including a variable delay line. The number of unit delay elements in the delay line can be selected to produce a desired output signal delay. Phase-mixing of multiple variable delay line outputs achieves finer delay-time adjustments.

Abstract: A delay circuit of a semiconductor device increases its delay time as an external voltage increases. The delay circuit can also ensure a desired delay time according to an external voltage, without additional delay circuits. The delay circuit of the semiconductor device includes a first delay unit, and a second delay. The second delay unit has a propagation delay characteristic different from that of the first delay unit with respect to variation of a power supply voltage, wherein the first delay unit is supplied with a first power supply voltage independent of variation of an external voltage, and the second delay unit is supplied with a second power supply voltage dependent on the variation of the external voltage.

Abstract: A delay locked loop (DLL) for generating a delay locked clock signal includes a delay line unit for delaying an external clock signal according to a delay amount control signal to thereby generate the delay locked clock signal; a divider for dividing the delay locked clock signal by a predetermined number determined based on a column address strobe (CAS) latency to thereby generate a divided signal; and a delay line control unit for generating the delay amount control signal based on a result of comparing a phase of the external clock signal and a delayed signal of the divided signal.

Abstract: A dual loop (PLL/DLL) data synchronization system and method for plesiochronous systems is provided. In particular, a system and method for dual loop data synchronization using a granular FIFO fill level indicator is provided. A dual loop data serializer includes a phase lock loop (PLL) and a delayed lock loop (DLL) configured with a phase shifter in the feedback path of the PLL. The dual loop serializer locks to the input of the DLL, which represents a fill level of a FIFO. A granular FIFO fill level indicator of the DLL provides input to the phase shifter to adjust the frequency of the PLL accordingly. Thus, the frequency of the data input rate can be controlled and a constant fill level of the FIFO can be maintained. A dual loop retimer includes a dual loop serializer (PLL/DLL) and a clock recovery DLL. The retimer resets the jitter budget to meet transmission requirements for an infinite number of repeater stages.

Abstract: The present invention provides a method and apparatus for updating serial devices. The apparatus includes a plurality of serial registers. The apparatus further includes a device adapted to provide a signal and a plurality of parallel registers, wherein each of the parallel registers is adapted to access at least one of the plurality of serial registers at substantially the same time in response to detecting the signal.

Abstract: The invention discloses an oscillator circuit (100, 200, 300, 400), comprising an oscillating element (110, 210, 310, 410) and output means (115, 215, 315, 415) for outputting an oscillation frequency from the oscillating circuit. The circuit further comprises a signal delay means (120, 220, 320, 420) which is arranged in series with the oscillating element and feeds the output signal back to the oscillating element. The delay means is (120, 220, 320, 420) tuneable with respect to the delay it provides. The oscillating element can be an amplifier or a VCO, and the delay means can be a Delay Locked Loop or a tuneable delay line, depending on the embodiment of the invention.

Abstract: An apparatus that reduces sampling errors for data communicated between devices uses phase information acquired from a timing reference signal such as a strobe signal to align a data-sampling signal for sampling a data signal that was sent along with the timing reference signal. The data-sampling signal may be provided by adjustably delaying a clock signal according to the phase information acquired from the strobe signal. The data-sampling signal may also have an improved waveform compared to the timing reference signal, including a fifty percent duty cycle and sharp transitions. The phase information acquired from the timing reference signal may also be used for other purposes, such as aligning received data with a local clock domain, or transmitting data so that it arrives at a remote device in synchronism with a reference clock signal at the remote device.

Abstract: A circuit and method for generating a local clock signal and a telecommunications system incorporating the circuit or the method. In one embodiment, the circuit includes: (1) a phase detector for receiving an input data signal, (2) (at least) first and second continuously controllable delay lines, coupled to the phase detector, for producing respective first and second candidate local clock signals and (3) delay line selector, coupled to the first and second delay lines, for selecting one of the first and second candidate local clock signals to be the local clock signal based on phase excursions in the input data signal.

Abstract: Circuits and methods for generating multi-phase clock signals using digitally-controlled hierarchical delay units (HDs) are provided. A plurality of serially-coupled HDs outputs clock signals that are phase-shifted relative to a reference clock signal. Each HD includes either one or two variable delay lines that provide coarse phase adjustment of an associated input signal. Each HD also includes one or more phase mixers that provide fine phase adjustment of the input signal.

Abstract: An apparatus for synchronizing signals. For devices, such as memory devices, implementing a synchronization device to synchronize signals, a synchronization device having a delay locked loop coupled to a phase locked loop may be implemented. The delay locked loop is implemented to measure the period of a reference signal and to mirror the period into a second delay line such that an adjusted reference signal having a frequency approximately equal to the frequency of the reference clock may be generated. The adjusted reference signal is delivered to an oscillator such that the oscillator begins oscillating at approximately the same frequency as the reference clock signal to provide a fast locking synchronization device.

Abstract: Methods and apparatus are provided for sigma-delta delay control in a Delay-Locked-Loop that employs a delay line to generate a clock signal based on a reference signal. A first value is generated if a clock signal has a time lead relative to a reference signal; and a second value is generated if a clock signal has a time lag relative to a reference signal. The first and second values are accumulated to generate an N bit digital word; and the N bit digital word is reduced to an M bit digital word, where M is less than N. Thereafter, the M bit digital word can be converted to an analog bias signal. The reducing step can be performed, for example, by a sigma-delta modulator. The high frequency quantization noise generated by the sigma-delta modulator can be filtered using a low pass filter. The converting step can be performed by a digital-to-analog converter, such as a master/slave digital-to-analog converter.

Abstract: A clock generator for generating an output clock signal synchronized with an input clock signal having first and second adjustable delay lines. The first adjustable delay lines is adjusted following initialization of the clock generator to expedite obtaining a lock condition following the initialization. The second adjustable delay line is adjusted after synchronization is achieved with the first adjustable delay line, or when the first adjustable delay line reaches a maximum adjustable delay. The first adjustable delay line is reset when a lock condition is initially obtained, and the second adjustable delay line is adjusted to compensate for the resetting of the first adjustable delay line.

Abstract: A pulse generator is provided for generating pulses with a selectable variable width and/or delay. The pulse generator comprises an oscillator and a selecting arrangement for selecting how many of a first group of delay elements are connected in series for delaying the oscillator signal. Identical delay elements are connected in series to form a second group. A measuring circuit repeatedly measures the delay provided by the second group, for example providing output pulses whose width or duration is equal to the delay. A reference pulse generator generates a series of reference pulses, each of which is a predetermined fraction of the oscillator period. A control circuit compares the measurement and reference pulses to generate an error signal that is fed back to timing delay control inputs of all the delay elements such that the widths of the measurement and reference pulses are made substantially equal to each other.

Abstract: One or more combinational circuits are connected to one or more flip-flop circuits. One or more clock buffers supply a clock to the flip-flop circuit. A control circuit controls a delay time of the flip-flop circuit and the combinational circuit independently each other.

Abstract: A delay-locked loop (DLL) circuit with mutual-interpolating architecture that provides multiple-phase clock generation is presented. Each delay-cell in the DLL circuit delay chain is effectively an interpolator that combines two input clock signals: one input clock signal is received from the output clock of previous stage in the delay chain, and the other input clock signal is fed back from a following stage. Each delay cell supports the concurrent functions of delay and interpolation. The architecture imposes a set of N simultaneous equations, where N is the total number of delay clock signals, to control the clock waveforms. These simultaneous equations obtain a unique solution when the DLL enters a lock state, and the generated delay clock signals inherently have a clock duty cycle of 50%. The delay chain can be implemented using either odd or even number of delay cells.

Abstract: The invention relates to an apparatus for precise modulation of signal phase and signal delay, respectively, and signal amplitude, comprising a first fixed-delay device having its input coupled to an input signal, a first variable delay device having its input coupled to said input signal and having a control input for delay adjustment, a first amplitude control device in series with the first variable delay device, providing at its output an amplitude controlled signal and having a control input for adjusting the output amplitude, a phase detector with linear characteristic having its two inputs connected to the output of the fixed-delay device and the output of the first amplitude control device, an error measurement device having its negative input connected to the output of the phase detector and its positive input connected to a control signal, an amplifier with low-pass characteristic having its input connected to the output of the error measurement device and its output to the control input of the firs

Abstract: A delay-locked loop apparatus includes at least a rising-clock delay-locked circuit, a falling-clock delay-locked circuit, and a duty cycle compensation circuit. The rising-clock delay-locked circuit detects the phase difference between a first clock inputted as a reference clock and a second clock obtained by replica-delaying the first clock, and then delay-locks the first clock and outputs a rising clock. The falling-clock delay-locked circuit detects the phase difference between an inverted clock of the first clock and the rising clock after a delay locking operation with respect to the rising clock, delay-locks an inverted clock of the first clock and outputs a falling clock. The duty cycle compensation circuit compensates duty cycles of the delay-locked rising clock and falling clock, and the falling-clock delay-locked circuit includes a divider for separately dividing the inverted clock and the delay-locked rising clock.

Abstract: A clock signal synchronizing method and an apparatus device for utilization with the synchronization of clock signals is disclosed. In one embodiment, the apparatus includes a delay device with a variably controllable delay time into which a clock signal, or a signal obtained therefrom, is input, charged with the variably controllable delay time, and output as a delayed clock signal. A device is provided for determining whether a clock edge of the delayed clock signal output by the delay device, or of a signal obtained therefrom, lies within a predetermined time window before a corresponding clock edge of the clock signal, or of the signal obtained therefrom.

Abstract: A duty cycle corrector includes a first controllable delay, a second controllable delay, a phase detector, and a compensation circuit. The first controllable delay is configured to delay a first signal to provide a second signal. The second controllable delay is configured to delay the second signal to provide a third signal. The phase detector is configured to adjust the first controllable delay and the second controllable delay to phase lock the third signal to the first signal. The compensation circuit is configured to compensate for a mismatch between the first controllable delay and the second controllable delay to provide a fourth signal in response to the first signal and a fifth signal approximately 180 degrees out of phase with the fourth signal in response to the second signal.

Abstract: An apparatus and method for generating phase-related clocks are disclosed. A clock input is delayed by an alignment magnitude to generate a first phase signal. The first phase signal is delayed by the phase alignment magnitude to generate a first phase delay signal. The clock input is delayed by a phase delay magnitude to generate a second phase signal and the second phase signal is delayed by about the phase delay magnitude to generate a last phase delay signal. A phase difference is detected between the first phase delay signal and the last phase delay signal and adjustments are made to at least one of the phase delay magnitude and the alignment magnitude.

Abstract: A DLL comprises detection circuitry configured to detect a too_slow and a too_fast operating state and correction circuitry configured to correct operation of the DLL when a too_fast or too_slow state is detected. The correction circuitry can be configured to swallow a pulse of the input clock signal when a too_fast condition is detected. The correction circuitry can also be configured to force the DLL into a too_fast operation state, when a too_slow operation state is detected. The correction circuitry can then also be configured to swallow a pulse of the input clock signal once the DLL is in the too_fast operation state.

Abstract: Control on the speed of operation of a delay loop from the output of a variable delay circuit to a delay control input thereof is performed. For example, frequency-dividing circuits are respectively placed at the input and output of the variable delay circuit. A signal obtained by frequency-dividing a signal outputted from the variable delay circuit is supplied to one input of a phase comparator through a dummy delay circuit, and a signal obtained by frequency-dividing the input of the variable delay circuit is supplied to the other input of the phase comparator. Phase control is performed according to the result of comparison between the phases of both signals. Control on the speed of operation of a delay loop from the output of a variable delay circuit to a delay control input thereof is performed. For example, frequency-dividing circuits are respectively placed at the input and output of the variable delay circuit.