Abstract: A PLL circuit includes a phase comparator which makes a comparison between an internal clock signal and a clock signal supplied from an external terminal, a charge pump circuit which produces a charging-up or discharging current in accordance with the output of the phase comparator, so as to drive a filter capacitor, a voltage-controlled oscillator the oscillation frequency of which is controlled by the held voltage of the filter capacitor, and a frequency divider circuit which generates the internal clock signal on the basis of the oscillation output of the voltage-controlled oscillator. The PLL circuit is additionally provided with a voltage detector circuit which detects whether the held voltage of the filter capacitor has been raised to a predetermined voltage or higher, and the function of forcibly lowering the held voltage of the filter capacitor down to a predetermined potential in accordance with the detection output of the voltage detector circuit.

Abstract: An over-sampling type clock recovery circuit includes a phase difference detecting section, a phase adjusting section and a signal selecting section. The phase difference detecting section detects a phase difference between a data signal and each of a plurality of active sets of clock signals, and generates a phase adjustment signal from a plurality of phase difference data corresponding to the detected phase differences using a majority determination. The phase adjusting section generates N (N is an integer equal to or larger than 2) sets of clock signals and adjusts phases of clock signals of the N sets based on the phase adjustment signal. The signal selecting section selects a part or all of the N sets of clock signals based on the detected phase differences from the phase difference detecting section. The selected sets of clock signals are supplied to the phase difference detecting section as the plurality of active sets of clock signals.

Abstract: An over-sampling type clock recovery circuit includes a phase difference detecting section (TIPD, CP, LFP), a phase adjusting section (VCO, VD, FD) and a signal selecting section (LDEC, SW). The phase difference detecting section (TIPD, CP, LFP) detects a phase difference between a data signal and each of a plurality of active sets of clock signals, and generates a phase adjustment signal from a plurality of phase difference data corresponding to the detected phase differences. The phase adjusting section (VCO, VD, FD) generates N (N is an integer equal to or larger than 2) sets of clock signals and adjusts phases of clock signals of the N sets based on the phase adjustment signal. The signal selecting section (LDEC, SW) selects a part or all of the N sets of clock signals based on the detected phase differences from the phase difference detecting section. The selected sets of clock signals are supplied to the phase difference detecting section as the plurality of active sets of clock signals.

Abstract: An integrated circuit (11) has a frequency detection circuit (22) which provides one or more digital signals (50) to a current source (26) based upon a detected frequency of operation of a generated reference clock (48). The signals (50) allows the current source (26) to change its operational state between two or more discrete current output levels in a digitally-controlled manner. Using signals (50), a high current output level can selected and provided by the current source (26) to the external oscillator circuit (16) during a start up mode to ensure that the integrated circuit (11) can start up in an optimally reduced time period. After a start up operation is complete, the signals (50) can then be used to switch the current source (26) into a lower current operational mode whereby electromagnetic interference (EMI) effects are reduced during the normal modes of operation occurring after start up.

Abstract: The object of the invention is to provide a lock-in process and device for a YIG-tuned oscillator which takes into account ageing and hysteresis of the YIG-tuned oscillator. This object is attained in that during a predetermined frequency change, the frequency of the YIG-tuned oscillator (1) is preset by means of a microprocessor (17) that progressively changes the current (I.sub.SP) in the main tuning coil (13) of the YIG-tuned oscillator (1) by an iterative capture routine, until the capture range (.DELTA.FM) of the switched-on frequency-locked loop, which changes with the coil current (I.sub.SP), includes the new operating frequency (f.sub.SET). The switched-on frequency-locked loop then pulls the oscillator frequency into the capture range of the PLL and the PLL locks-in the oscillator frequency to the new operating frequency (f.sub.SET). The microprocessor (17) interrupts the capture routine when a PLL-LOCK detector (11) announces to the microprocessor (17) that the new operating frequency (f.sub.

Abstract: A phase-locked loop circuit with dynamic backup is disclosed. The phase-locked loop circuit with dynamic backup includes a phase comparator, a lowpass filter, a voltage-controlled oscillator, and a detection circuit. The phase comparator compares an input reference signal and a feedback output signal from an output of the phase-locked loop circuit for generating a voltage signal representing the phase difference between the input reference signal and the feedback output signal. After the voltage signal is filtered by the lowpass filter, the filtered voltage signal is sent to the voltage-controlled oscillator for generating the feedback output signal. Coupled to the phase comparator, the detection circuit detects whether or not the phase-locked loop circuit is in lock with the input reference signal.

Abstract: A phase comparator compares phase of a clock signal and a generated comparison clock signal based upon rising edges. The output of the phase comparator may include a series of short up (U) pulses or down (D) pulses, depending whether the phase of the comparison clock is leading or lagging the clock. Up and down pulses U and D control an up/down shift register which in turn compensates phase difference by inserting or removing additional discrete delay elements in a variable delay line. Based upon delay signals generated by the variable delay line, a double frequency clock generator generates a 2.times. clock signal. The 2.times. clock signal is divided by 2 in a divider to supply the phase comparator with the generated comparison clock signal. The feedback scheme helps the digital delay lock loop of stabilize after a few clock cycles without additional external control.

Abstract: A segmented dual delay-locked-loop (DLL) has a coarse DLL and a fine DLL. Each DLL has a series of buffers, a phase detector, charge pump, and bias-voltage generator. The bias voltage controls the delay through the buffers. The bias voltage of the coarse DLL is adjusted by the phase comparator to lock the total delay through the buffers to be equal the input-clock period. The coarse DLL divides an input clock into M equal intervals of the input-clock period and generates M intermediate clocks having M different phases. An intermediate mux selects one of the M intermediate clocks in response to a phase-selecting address. The selected intermediate clock K and a next-following intermediate clock K+1 are both selected and applied to the fine DLL. The K clock is input to a series of N buffers in the fine DLL while the K+1 clock is directly input to a phase detector. The phase detector compares the K+1 clock to the K clock after the delay through the buffers.

Abstract: A logic analyzer uses a single tapped delay line and a single array of sampling cells for high speed digital signal acquisition, by controlling both edges of a substantially 50% duty cycle clock signal to drive a delay line buffer chain. The chain operates continuously; there being no need for interruptions for precharge intervals. Thus, the need for a second delay line buffer chain is eliminated.

Abstract: An apparatus comprising a phase-locked loop, a select circuit and a control circuit. The phase-locked loop may be configured to generate a feedback signal (along with a buffered output signal) in response to a reference clock and a control signal. A select circuit may be configured to present a reference clock signal in response to a plurality of input clock signals and a select signal. The slew control circuit may be configured to generate the control signal in response to the select signal, and the feedback signal. The control circuit may be used to reduce noise presented to the phase-locked loop and may allow for a rapid initial frequency acquisition of the PLL to the reference frequency.

Abstract: In a PLL circuit, the phase of the frequency of an input signal is compared with that of an oscillation frequency generated from a voltage-controlled oscillator. Charge pump circuits are provided which outputs currents pulse-width modulated based on information about the error between the two phases, respectively. An output voltage of a capacitor provided at a stage subsequent to one of the charge pump circuits is converted into a current by a gm amplifier. Further, the converted current is added to an output current of the other charge pump circuit. The so-added output is used as a control input for the voltage-controlled oscillator. The oscillation frequency of the voltage-controlled oscillator is produced as an output signal frequency.

Abstract: A circuit comprising an oscillator, a multiplexer, a half rate clock circuit and a full rate clock circuit. The oscillator may be configured to generate a first clock signal and a second clock signal in response to a control signal. The multiplexer may be configured to generate the control signal in response to (i) a half-rate clock signal and (ii) a full rate clock signal. The half rate clock circuit may be configured to generate the half rate clock signal in response to the first and second clock signals. The full rate clock circuit may be configured to generate the full rate clock in response to (i) one of the first and second clock signals and (ii) a reference clock.

Abstract: A phase locked loop unlock detector is provided for a data detection channel in a direct access storage device (DASD). The phase locked loop unlock detector includes a counter for generating a threshold reference relative to a reference signal. An unlock window generator is coupled to the counter for generating an unlock window signal. An unlock error detector is coupled to the unlock window generator for comparing a variable frequency signal with the unlock window signal.

Abstract: Disclosed is the drive apparatus for the powder feeder, which has; the duty ratio control circuit 12 which applies the alternating voltage with the resonance frequency to the vibrator 10 during a time corresponding to the duty ratio; the current monitor 15 which detects the residual frequency of the electro motive force produced due to the residual oscillation of the vibrator 10 when the alternating voltage with the resonance frequency is not applied from the duty ratio control circuit 12 and feeds back the detected residual frequency to the PLL control circuit 11 through the zero-cross comparator 17.

Abstract: A phase locked loop ("PLL") 28 containing apparatus for automatically causing the PLL to achieve phase lock when first energized or after having lost phase lock. In addition to a phase detector 4, loop filter 13, voltage controlled oscillator ("VCO") 14 and feedback from the VCO to the phase detector 16, the PLL has a sweep circuit 30. The sweep circuit cooperates with the loop filter when the PLL is not in phase lock to automatically generate a control voltage for the VCO which control voltage increases linearly with time until the PLL achieves phase lock or until the control voltage has reached the largest voltage in the dynamic input range of the VCO. In the event that phase lock is not achieved during the period of the increasing voltage, the control voltage decreases linearly with time to drive the PLL into phase lock.

Abstract: A phase locked loop (PLL) circuit performs a frequency pull-in operation with a simple structure. The PLL circuit has an oscillating part which oscillates at a frequency corresponding to a control input signal and a phase comparing part which detects a phase difference between an oscillation output signal of said oscillator and an input frequency signal and produces an error signal responsive to a detection value. The PLL circuit further includes a forcible pull-in part which adds values of the error signal and a forcible pull-in signal, and provides a signal based on a result of addition as the control input signal. The forcible pull-in circuit includes a reference value generating circuit which supplies a reference value determining a unit change width of an oscillation signal of the oscillating part, and a computing part which computes a value of the forcible pull-in signal based on the reference value.

Abstract: For a possible simple structure, dispensing with ceramic filters, an FM demodulator for demodulating sound-FM signals comprises a controllable amplifier (1) which receives the sound signals converted to intermediate frequencies, said amplifier having a gain which is adjusted by means of an amplitude control circuit (4) and whose output signal is applied to the amplitude control circuit and to the phase-locked loop which supplies a demodulated sound signal in the locked-in state from its output, said phase-locked loop including a loop filter (7) which comprises a filter (8, 9, 10) of at least the second order with a pole at the frequency f=0, and a limit-detection circuit (13) which feeds back the operating frequency of the phase-locked loop to a predetermined frequency range when said phase-locked loop leaves this frequency range around a predeterminable nominal demodulation frequency, the amplitude control circuit (4) controlling the controllable amplifier (1) in dependence upon its output signal and a signa

Abstract: The invention relates generally to transmission of digitized information and more specifically to a digital receiver locking device that provides a decreased lock-in time and minimizes requirements to a permissible frequency and phase matching error. Outputs of a digital phase detector 1 are coupled, respectively, to an addition input of an analog adder 2 and a first information input of a multiplexer 3 having an output coupled to a subtraction input of the analog adder 2. An output of the adder 2 is connected via a low-pass filter to an input of a voltage controlled oscillator (VCO) 5 having an output connected to a clock input of a decision unit 6 whose information input is coupled, along with a first input of the phase detector 1 and a first input of a lock state detection circuit 7, to an input of the locking device. A second input of the phase detector 1 and a clock input of the decision unit 6 are coupled to an output of the VCO 5.

Abstract: A circuit is provided for controlling or regulating a phase-locked loop (PLL) output during times when the PLL is unlocked. Noise or corruption on the input signal of the PLL may cause the PLL output frequency to suddenly rise to match the input signal frequency. In many instances, the noise or corruption cannot be filtered by the low pass filter within the PLL. A detection circuit is coupled to receive the input signal, and discern times in which non-filterable noise occurs. The detection circuit may include a decoder which decodes, e.g., error correction coding within the input signal data stream to indicate possible instances in which the PLL will unlock. Once the detection circuit indicates an unlock condition and forwards an unlock selection signal to a multiplexer, the multiplexer chooses a frequency divided clocking signal rather than the PLL output clocking signal.

Abstract: A wide band phase locked loop using a narrow band voltage controlled oscillator is provided. The wide band phase locked loop circuit includes a frequency and phase detector for generating a signal corresponding to a difference in a frequency and a phase between an input signal and a reference signal and a loop filter for filtering the signal generated by the frequency and phase detector to a predetermined frequency band. The filtered signal from the loop filter is provided to a narrow band voltage controlled oscillator which generates a signal having a frequency varying according to a voltage of the filtered signal, and a level detector which generates dividing ratio control information by detecting a voltage level of the filtered signal. A variable frequency divider generates the reference signal by dividing the signal generated from the voltage controlled oscillator by a dividing ratio determined according to the dividing ratio control information.

Abstract: A phase lock loop circuit. The phase lock loop circuit includes first and second pass gates. The pass gates include signal inputs that receive first and second reference signals, respectively. The pass gates also have enable inputs. The phase lock loop also includes a loop filter that is coupled to the outputs of the first and second pass gates. A loop oscillator is coupled to the output of the loop filter. A strobe circuit is coupled to the output of the loop oscillator. The strobe circuit provides an input signal to the enable inputs of the first and second pass gates so as to sample the first and second reference signals. The loop filter uses the samples of the first and second reference signals to create a control signal that forces the loop oscillator to output a signal with a phase that is between the phases of the first and second reference signals.

Abstract: A method for removing an external frequency divider and clock formation circuit from a feedback path of a phase locked loop and a phase selector circuit are provided for synchronizing an external frequency divider with a reference clock of a phase locked loop. A reference clock signal is applied to the phase locked loop. An output of the phase locked loop is coupled through a predefined delay and provides a delayed feedback clock signal input to the phase locked loop. The external frequency divider is located at the output of the phase locked loop external to the predefined delay and outside the feedback clock signal path of the phase locked loop. A phase selector circuit identifies a correct phase of the reference clock signal and starts the external frequency divider. The phase selector circuit includes an edge detector, a synchronization divider, and a reset machine.

Abstract: In the present invention, when a phase comparison circuit, which compares the phase of a reference clock divided by a frequency divider that frequency divides a supplied clock, to that of a variable clock, detects the phase-matching of the two clocks, it generates a phase synchronization detection signal, and this phase synchronization detection signal increases the frequency division ratio of a frequency divider, lowering the frequency of operation of the phase comparator. The present invention is further characterized in that, at reset, when an inactive state becomes an active state, the time required to phase synchronize both clocks is shortened by resetting the above-described phase synchronization detection signal, thereby setting the frequency division ratio of the frequency divider to its original low state, and the frequency of operation of the phase comparator to its original high state.

Abstract: A PLL (phase lock loop) circuit improves pull-in and noise performances by changing a loop gain based on the loop states. The PLL circuit includes a voltage controlled oscillator (VCO) for generating an oscillation signal whose oscillation frequency is controlled by a control voltage provided thereto, a phase comparator for detecting a phase difference between the oscillation signal from the VCO and a reference signal wherein a detection gain of the phase difference is regulated by a bias voltage provided thereto, a low pass filter for receiving an output signal of the phase comparator for removing high frequency components therefrom to produce the control voltage supplied to the VCO, a phase lock loop formed by the VCO, phase comparator and low pass filter, and a phase lock detection circuit for detecting whether the phase lock loop has reached a phase lock state and changing the bias voltage to decrease the detection gain of the phase comparator when the phase lock loop has reached the lock state.

Abstract: A digital delay circuit and a digital PLL circuit achieve reduction in size and power consumption. Each of a first delay line (301) and a second delay line (302) includes a plurality of delay elements. A control circuit (200) selects the delay element(s) included in a delay line (300), and a second clock signal (S11) passes only through the selected delay element(s). That is, the second clock signal (S11) does not pass through the non-selected delay element(s), which reduces power consumption.

Abstract: A lock detector for a phase locked loop circuit, wherein an oscillator is controlled by a control signal produced by comparing the output signal of the oscillator to a reference signal. The lock detector samples the control signal, examines a plurality of samples according to criteria associated with a prescribed lock condition between the reference signal and the oscillator output signal, and generates a lock signal indicative of the lock condition being met if the samples satisfy the criteria. In a favorable embodiment, the lock detector forms a first group of samples sampled at a rate controlled by the reference signal and a second group of samples sampled at a rate controlled by the oscillator output signal. The samples are stored and shifted at the respective rates in respective shift registers. The contents of each stage of the shift registers are then examined according to a logic function.

Abstract: A circuit comprising a plurality of phase locked loop circuits, a control circuit and a plurality of storage elements. Each of the plurality of phase locked loop circuits may present a recovered data signal and a recovered clock signal in response to one of a plurality of serial data streams, a clock signal and one of a plurality of indication signals. The control circuit may present a counter signal in response to the recovered clock signals. The plurality of storage elements may each be configured to present one of the indication signals in response to the clock signal, a select signal and the counter signal.

Abstract: A known phase-control loop comprises an oscillator having a controllable frequency, a frequency divider and a phase comparator which compares a reference signal (CKREF) with the signal at the output of the frequency divider and controls the frequency of the oscillator.The circuit also comprises, at the output of the oscillator, a phase shifter which supplies a signal (CKN0) at a multiple frequency of the input frequency and shifted in phase with respect to the signal of the oscillator, and a synchronizing module which may be simply constituted by a D flipflop with the input D connected to the output of the divider, and the input CLK connected to the output of the phase shifter, and which supplies a signal (CKREF0) at the frequency of the input signal (CKREF) but is locked at the output signal of the phase shifter.

Abstract: A semiconductor device (e.g., a zero-delay buffer) is provided which is capable of reducing current or power consumption without the use of a dedicated pin. The device may include a frequency detector that receives a detector input signal corresponding to or derived from a device input signal. The device input signal performs a first function during normal operation of the device. The detector determines whether the frequency of the detector input signal is less than a predetermined minimum, and if so, generates a power down signal configured to direct the device to reduce current or power consumption in at least one of its component circuits. The frequency detector may include a "one-shot" circuit responsive to the detector input signal for generating a frequency indicator signal, and a "power down" signal output circuit responsive to the frequency indicator signal for generating the power down signal.

Abstract: A lock detector (16) includes a set circuit (64), a reset circuit (120), and a latch circuit (80). The latch circuit (80) provides an output signal (82) in response to the temporal relationship of the first input signal (12) and the second input signal (14). The set circuit (64) initiates the transition of the latch circuit (80) to the locked state, while the reset circuit (120) initiates the transition of the latch circuit (80) to the not-locked state.

Abstract: The present invention supplies a first delay control signal generated by a DLL circuit to a first variable delay circuit which generates a control clock by delaying a clock for a prescribed time period. The DLL circuit comprises: a first delay loop, comprising a second variable delay circuit and a third variable delay circuit connected in series, to which the clock is supplied; a phase comparator which is supplied with a clock which delays an integral factor of 360.degree. of said clock from the clock, as a reference clock, and the output of the first delay loop, as a variable clock; and a delay control circuit which generates said first delay control signal in accordance with a phase comparison result signal from the phase comparator such that there is no phase difference with said two supplied clocks. The second variable delay circuit is supplied with the first delay control signal. The third variable delay circuit has a delay time of .beta..degree.

Abstract: An oscillation circuit stops the oscillation of an external oscillator to reduce the current consumed when a frequency lower than the inherent frequency of the external oscillator is supplied to a microcomputer. A PLL circuit 37 generates a second clock 45 from a first clock 23 output by an oscillation circuit 1. A PLL lock signal 47 is changed from a first level to a second level when the second clock 45 is generated. A selector 39 outputs the second clock 45 as an internal clock 13 when the PLL lock signal 47 is at the second level. The operation of an oscillator 9 is stopped when the PLL lock signal 47 is at the second level.

Abstract: A phase lock loop includes precision charge pump current generation circuit which provides a dynamically variable charge pump current to a charge pump. The charge pump current is developed from the VCO control voltage and varies in inverse proportionality to changes in the control voltage. The proportionality between the precision current and the control voltage is defined by a bias network and such that the current is inversely proportional to the VCO gain and the phase lock loop bandwidth is therefore maintained at a substantially constant value.

Abstract: An apparatus and method for reducing spurious sidebands in the tuning signal of phase locked loop frequency synthesizers and phase locked loops is disclosed. The frequency synthesizer includes an oscillator, a divider, a difference circuit and a sampling circuit. The oscillator produces a variable frequency oscillator signal in response to an applied tuning signal. The divider divides the variable frequency oscillator signal by a division factor to produce a reduced frequency signal. The difference circuit receives the reduced frequency signal to produce a difference signal corresponding to the phase difference between the reference signal and the reduced frequency signal. The sampling circuit intermittently samples the difference signal in response to a timing signal to produce a tuning signal which approaches a DC characteristic. The tuning signal serves to adjust the oscillator frequency in a direction to diminish phase differences in the reference signal and the reduced frequency signal.

Abstract: To provide a PLL circuit with little jitter and a minimum frequency drawing time, a PLL circuit comprises: a phase comparator for generating an up-down signal, which is turned to logic HIGH when a reference clock signal is phase-advanced to an output clock signal and a phase lock signal, indicating synchronization of the output clock signal to the reference clock signal; a timing signal generator for generating a timing signal when the phase lock signal is generated for a certain period after said timing signal generator is initialized with a reset signal; an up-down counter for generating a count value which is incremented when the up-down signal is at logic HIGH and decremented when the up-down signal is at logic LOW according to each pulse of a count clock, memorizing the count value in a nonvolatile memory when controlled by the timing signal, and outputting the memorized count value when initialized by the reset signal; a D/A converter for outputting a control voltage in proportion to the count value; an

Abstract: A fractional-N phase-lock loop (PLL) with a delay line loop (DLL) having a self-calibrating fractional delay element which controls the PLL feedback signal in such a manner that the delay intervals for the feedback signal are: increased when small fractional divisors (<1/2) causing a lagging phase relationship or large fractional divisors (>1/2) causing a leading phase relationship are sensed; and decreased when small fractional divisors (<1/2) causing a leading phase relationship or large fractional divisors (>1/2) causing a lagging phase relationship are sensed.

Abstract: A lock circuit for indicating a locked/unlocked condition of phased lock loops circuits, which uses a reference clock signal input to a good-cycle counter and to a bad-cycle counter to signal a set/reset latch to output a signal indicating whether or not the phase of the output signal and input clock are in phase. Phase detector inputs are XOR gated to produce a pulse when the phase locked output clock is in a bad cycle indicated by the phase locked output clock not being in-phase with its input clock. Pulses on the XOR gate output on a bad cycle feed a single cycle counter reset circuit. The single cycle counter reset circuit on every cycle resets one of the bad and good counters based on its detection of a bad cycle pulse from the XOR gate. The good-cycle counter's output is to the SET input of the set/reset latch, and the bad-cycle counter's output is to the RESET input of the set/reset latch . We enable specific cycling of both the good and bad counters.

Abstract: An improved phase locked loop (PLL) circuit is provided for use in microprocessor clock generation. A ring oscillator provides an output frequency signal. A voltage to current converter converts differential control voltages to a variable reference current applied to the ring oscillator. A range control reference current generator applies a range control reference current to the ring oscillator. A range control operatively controls the range control reference current generator to sequentially change the range control reference current applied to the ring oscillator. A lock detector coupled to the range control compares the output frequency signal and a reference frequency signal and responsive to the compares signals applies a locked signal to the range control. Responsive to an applied locked signal, the range control stops changing ranges. The phase locked loop (PLL) circuit automatically sweeps through multiple frequency subranges responsive to the range control.

Abstract: A phase-locked loop (PLL) circuit capable of attaining high-speed frequency transition with enhanced reliability. To this end, outputs of a reference signal source (1) and voltage-controlled oscillator (VCO) circuit (3) are frequency-divided by frequency divider circuits (2, 4), respectively. A phase comparator circuit (5) is provided for outputting an error signal indicative of a phase difference between these signals, if any. A window generator circuit (9) is connected for outputting a window signal; where the error signal does not fall within the range of a pulse width of this window signal, a level generator circuit generates a boost voltage having its potential near the control voltage value of the VCO (3) for use in generating of a target frequency.

Abstract: A digital counter comprised of a synchronization judgement circuit and a counting circuit, the synchronization judging circuit receiving as an input signal the results of a comparison from a phase comparison circuit which compares the phase of a reference signal and an output signal of a frequency factoring circuit and outputting a phase synchronization judgement signal to the counting circuit, the counting circuit receiving as input the results of comparison and the phase synchronization judgement signal, performing a count based on the results of comparison, and successively determining a count from the most significant bit to the least significant bit. Also, a digital PLL circuit using the digital counter.

Abstract: A phase lock loop for recovering a bit clock from a signal containing variations in the bit rate includes mans for resetting the frequency of said phase lock loop to a preset value if the loop loses its lock or if adverse conditions are detected. The loop may be reset if the frequency passes a preset limit or if other apparatus responsive to signal quality or signal to noise ratio detects adverse conditions. In one embodiment the signal is also subjected to automatic gain control and to adaptive filtering, and the frequency may be reset if the A.G.C. and/or the adaptive filter coefficients pass preset thresholds.

Abstract: A mixed signal phase locked loop is optimized for fast settling and low noise sensitivity. To this end, this device has a digital wide range delay line and a low gain per stage adjust. When first activated, the loop calibrates the digital delay line to its nominal delay characteristic. This delay line, together with the linear low gain per stage adjust, constitutes the internal oscillator of the phase locked loop. After achieving nominal delay, the oscillator uses the low gain per stage adjust to lock to a desired reference or a submultiple thereof. According to the preferred embodiment, the loop locks its internal 125 MHz oscillator to a 25 MHz reference. After achieving lock, the loop performs synchronous data recovery by locking to an incoming data stream, instead of the internal reference, and performing bit framing. In case of losing lock, the phase locked loop of the present invention is capable of recalibrating itself and regaining lock in under 3 microseconds.

Abstract: A PLL synthesizer includes a reference oscillator, an controllable oscillator which generates an oscillation signal which varies in frequency according to a control signal, a phase comparator, and a loop filter. The loop filter includes an A/D converter, a digital filter, and a D/A converter. The digital filter removes high-frequency components from the output of the A/D converter according to setting data. The digital filter is set to a filter characteristic depending to a selected frequency of the oscillation signal. The digital output signal of the digital filter is converted to an analog signal which is used as the control signal of the controllable oscillator.

Abstract: A circuit for enabling and disabling generation of an output clock signal is disclosed. The circuit includes a PLL lock detect circuit that generates an active lock control signal when an output reference signal of a phase lock loop (PLL) circuit is phase locked relative to an input reference signal to the PLL. The output reference signal of the PLL, and the lock signal from the lock detect circuit, are both provided to a clock enable circuit. The clock enable circuit includes a negative edge-triggered D-type flip-flop and a two-input AND gate. The lock signal is applied to the D-input of the flip-flop, while the clock signal is applied to the clock input of the flip-flop. The lock signal is generated asynchronously relative to the input clock signal. Therefore, the flip-flop samples the lock signal on each falling edge of the clock signal so as to synchronize the lock signal relative to the input clock signal.

Abstract: A method and circuitry for detecting when a PLL achieves phase and frequency-lock to a reference frequency with minimal hardware and power dissipation are disclosed. The invention takes advantage of existing blocks within a PLL to reduce the amount of circuitry required while at the same time reducing error due to mismatch. In one embodiment, the present invention combines a coarse lock-detect circuit with a fine lock-detect circuit to achieve fast response when the input reference is lost, while filtering occasional minor phase hits due to external or internal noise.

Abstract: In a PLL circuit, the phase of the frequency of an input signal is compared with that of an oscillation frequency generated from a voltage-controlled oscillator. Charge pump circuits are provided which outputs currents pulse-width modulated based on information about the error between the two phases, respectively. An output voltage of a capacitor provided at a stage subsequent to one of the charge pump circuits is converted into a current by a gm amplifier. Further, the converted current is added to an output current of the other charge pump circuit. The so-added output is used as a control input for the voltage-controlled oscillator. The oscillation frequency of the voltage-controlled oscillator is produced as an output signal frequency.

Abstract: A method for detecting a locked condition of a demodulator of at least one signal that may have discrete levels defining a constellation of nominal points in a plane. The method includes the steps of defining reference areas about the nominal points, a reference area being separated from another by a band or an angular sector crossing the origin of the constellation plane, and indicating a locked condition if the ratio of points occurring in the reference areas is above the probability for points to occur in the reference area, when the demodulator is wrongly adjusted.

Abstract: A phase-locked loop includes a switched phase detector, a loop filter and an oscillator connected in series, as well as a device for technology compensation, in particular a course control device. An operating point is adjusted during a starting phase of the phase-locked loop through the use of the course control device in such a way that the damping and natural frequency of the phase-locked loop is independent of fluctuations in technology parameters.

Abstract: The invention provides a phase synchronization system which stops, when an input of a phase reference signal from the outside stops, oscillation of a voltage-controlled oscillator to achieve reduction in power consumption and can produce and output a system clock signal free from high frequency pulse noise from the voltage controlled oscillator. The system includes a phase comparator, a phase synchronization circuit including a low-pass filter and a voltage-controlled oscillation circuit, a clock detection circuit for detecting the clock signal from the outside, a phase coincidence discrimination circuit for discriminating a phase coincidence condition at the phase synchronization circuit, an AND gate, and a stop/start control circuit including a pair of flip-flop circuits. When the clock signal from the outside stops, oscillation of the voltage-controlled oscillation circuit is stopped with control information from the stop/start control circuit.

Abstract: A phase-locked-loop device for generating an output signal of frequency Fo, n phase-lock with an input signal of frequency Fi, where Fo=N(Fi/M). The invention reduces noise and provides optimal-time frequency switching--settling in one cycle of the phase-detector reference signal by applying a signal shaped like a smooth broad hump to the voltage-controlled oscillator upon a frequency change command. It maintains optimal-time switching by keeping the PLL loop-gain constant. The invention reduces noise by eliminating the so called "dead-zone" in the digital phase-detector.