Abstract: A digital phase shift amplification and detection system and method. A signal is applied to a digital phase shift amplifier including a flip flop operated in the metastable region which amplifies any timing changes in the signal. The amplified signal is fed into a detection circuit configured to detect timing delays in the amplified signal. In one embodiment, the present invention relates to a digital phase shift amplification and detection system and method. A signal is applied to a digital phase shift amplifier including a flip flop operated in the metastable region which amplifies any timing changes in the signal. The amplified signal is fed into a detection circuit configured to detect the amplified timing differences in the amplified signal as a result of a relatively smaller timing change in an input signal. The detection circuit is coupled to clock signals that are out of phase with the clock signal that triggers the metastable flip flop in the phase shift amplifier.

Abstract: In a first aspect, a lock indicator circuit is disclosed. The lock indicator comprises a first circuit for providing a first beat signal; and a second circuit for providing a second beat signal. A reference clock signal and a recovered clock signal are provided in a reversed manner to the first and second circuits. In a second aspect, a method for providing a lock indication of a circuit is disclosed. The method comprises the steps of providing a first and second beat signals; and utilizing the first and second beat signals to determine if a lock condition has occurred. A system and method in accordance with the present invention indicates a lock to the desired reference clock and provides an error or out of lock condition if the recovered frequency is at a harmonic or subharmonic of the reference frequency. This ability to avoid a false lock indication requires very little additional circuitry.

Abstract: A method and an apparatus relating to a PLL circuit for frequency synthesizer applications. By using a composite PFD large and small phase variations between a reference signal and the divider output are compensated for. The composite phase frequency detector (PFD) has both a digital phase frequency detector (digital PFD) and an analog phase detector (analog PD) with the digital PFD compensating for large phase differences and the analog PD compensating for smaller phase differences. The PLL automatically chooses between these two components in the composite PFD by controlling the pulse width of the divider output. This is accomplished by synchronizing the dead zone of the digital PFD with the active pulse width of the divider output and by similarly synchronizing the phase detector window of the analog PD to be within both the dead zone of the digital PFD and the active pulse width of the divider output.

Abstract: A three state phase frequency lock detector (14) is provided which monitors the UP and DOWN phase pulses generated by a three state phase frequency detector (PFD). The lock detector (14) asserts the lock detect signal when the rising edges of the UP and DOWN phase pulses are phase aligned and un-asserts the lock detect signal for all other relative phases of the UP and DOWN phase pulses. Lock detector (14) is capable of reporting the lock detect signal for each cycle of the UP and DOWN pulses.

Abstract: A clock recovery circuit includes a sampling phase detector and frequency detector. The sample values generated in the phase detection portion of the clock recovery circuit and applied as inputs to the frequency detector to allow for frequency “cycle slips” to be detected and corrected without requiring the use of a separate circuit.

Abstract: A phase detector wherein binary signals are supplied to inputs of an asymmetric circuit having two EXOR elements, the output voltage of the phase detector being proportional to the phase difference between the input signals by a subtraction of the output signals of two EXOR elements and subsequent low-pass filtering, and the subtraction is conducted in such a manner that there is no longer an error, due to the internal propagation delays of the EXOR elements, for determining the phase difference. In particular, the equal-phase condition between the input signals is determined accurately and by a simple voltage comparison with a threshold value selected by the expert, and the range of determination of greater phase differences between binary signals can be extended by the circuit proposed.

Abstract: The detection circuit comprising: a first D-type flip-flop circuit F/F1, to which the data signal D1 and the clock signal C1 are input; a first delay circuit DL2 which delays the clock signal C1 by a prescribed amount of time, so as to generate a delayed clock signal C1′; a second D-type flip-flop circuit F/F2, to which the output signal Q1 of the first D-type flip-flop circuit F/F1 and the delayed clock signal C1′ are input; a second delay circuit DL1 which delays the an output signal Q2 of the second D-type flip-flop circuit F/F2 so as to generate a first delayed signal Q2′, a third delay circuit DL3 which delay the an output signal Q1 of the first D-type flip-flop circuit F/F1 so as to generate a second delayed signal Q1′, a fourth delay circuit DL4 which delays the data signal D1 so as to generate a delayed data signal D1′, a first AND circuit AND2 which calculates a logical product of the first delayed signal Q2′ and the second delayed signal Q1′ so as to output

Abstract: Phase detection circuitry is disclosed that can detect phase differences from a quadrature phase relationship, without requiring extensive additional circuitry for driving and correcting the phase detection circuitry. The phase detection circuitry can measure plural or multiple pulse durations consecutively, without interruption to reset the circuit or store the values generated by the circuit, affording a much higher sampling rate and sampling a higher proportion of pulses than is conventional. Averaging of the phase data samples is also provided by measuring multiple pulses, so that phase changes are not instigated based upon a signal from an individual pulse duration that may differ significantly from the average. In addition to detecting quadrature phase relationships, the phase detection circuitry can be adjusted to compensate for a desired offset in one of the signals from quadrature, or can be set to detect other phase relationships.

Abstract: A circuit comprising a first circuit and a state machine. The first circuit may be configured to generate a plurality of state inputs in response to (i) a first clock signal, (ii) a second clock signal delayed from the first clock signal, and (iii) a data signal. The state machine may be configured to generate a pump up signal and a pump down signal in response to (i) said data signal and (ii) a plurality of quadrants defined by a number of possible combinations of the state inputs. The state machine may be further configured to transition between any of the quadrants.

Abstract: In a feedback system such as a PLL, the integrating function associated with a loop filter capacitor is instead implemented digitally and is easily implemented on the same integrated circuit die as the PLL. There is no need for either an external loop filter capacitor nor for a large loop filter capacitor to be integrated on the same integrated circuit die as the PLL. In a preferred embodiment, an analog phase detector is utilized whose phase error output signal is delta-sigma modulated to encode the magnitude of the phase error using a digital (i.e., discrete-time and discrete-value) signal. This digital phase error signal is “integrated” by a digital integration block including, for example, a digital accumulator, whose output is then converted to an analog signal, optionally combined with a loop feed-forward signal, and then conveyed as a control voltage to the voltage-controlled oscillator.

Abstract: A receiving circuit for receiving a signal transmitted to a signal transmission path, the receiving circuit comprising: a signal potential detection means for detecting signal potential of the received signal, a signal logic value discrimination means for discriminating a logic value of the received signal, and a reference signal generation means for generating a reference signal for the signal logic value discrimination means, based on a signal potential detected by the signal potential detection means and a discrimination result of the signal logic value discrimination means.

Abstract: A phase detector including a voltage controlled oscillator generating a voltage controlled oscillator output, and a first logic state device for receiving said voltage controlled oscillator output as an input. The phase detector also includes a reset device, for generating a reset signal to reset the first logic state device such that the output control signal of the first logic state device reaches a low level in response to a first edge of the reset signal.

Abstract: A phase detector is disclosed that detects the phase of two inputs with precision. A method and apparatus of phase detecting that subtracts out common errors due to temperature variations and supply voltage fluctuations. The phase detector and method preferably utilize digital circuitry such as exclusive OR gates and differential amplifiers to perform the accurate phase detection. The inputs and outputs may be attenuated or filtered to produce the desired results.

Abstract: A phase locked loop (PLL) is use in a radio communication system such as a frequency mixer, a carrier frequency and the like. The phase locked loop (PLL) includes a phase/frequency detector for comparing a phase/frequency of a reference signal and a feedback signal. The phase/frequency detector includes: a NAND gate logic circuit for NANDing a first signal and a second signal to output a NANDed signal; a first latch unit for latching the NANDed signal and outputting the first signal in response to a reference frequency; and a second latch unit for latching the NANDed signal and outputting the second signal in response to a feedback frequency. The phase locked loop (PLL) further includes a filter controller for changing a bandwidth of a low pass filter in response to an output signal of the phase/frequency detector.

Abstract: The present invention relates generally to the field phase detectors and particularly to a phase detector being formed by a flip-flop.

Abstract: A phase detector which detects the phase difference between the input clock and an output clock. That phase difference is used to gate a high frequency clock, which is provided to an integration circuit. The phase detector also indicates whether the phase difference is positive or negative. The output of the integration circuit is provided to a comparator, which compares the value to a threshold. When the threshold is exceeded, an advance or retard signal is provided to a phase selector. The phase selector selects one of multiple phases of a clock used for the output clock.

Abstract: A phase locked loop (PLL) is used in a radio communication system such as a frequency mixer, a carrier frequency and the like. The phase locked loop (PLL) includes a phase/frequency detector for comparing a phase/frequency of a reference signal and a feedback signal. The phase/frequency detector includes: a NAND gate logic circuit for NANDing a first signal and a second signal to output a NANDed signal; a first latch unit for latching the NANDed signal and outputting the first signal in response to a reference frequency; and a second latch unit for latching the NANDed signal and outputting the second signal in response to a feedback frequency. The phase locked loop (PLL) further includes a filter controller for changing a bandwidth of a low pass filter in response to an output signal of the phase/frequency detector.

Abstract: A frequency comparator includes a circuit comparing, independently of a phase relationship between first and second clocks, frequencies of the first and second clocks and outputting first and second detection signals when the first clock has frequencies higher and lower than those of the second clock, respectively. The first and second detection signals are output for respective times based on a difference between the frequencies of the first and second clocks.

Abstract: A phase comparator for comparing the relative phase of a first input signal and a second input signal. The phase comparator detects a slipping condition, the slipping condition present if the first input signal leads the second input signal in phase and the first input signal is delayed for at least one cycle such that a first rising edge of the first input signal lags a first rising edge of the second input signal by greater than 180°. The phase detector resets at least one output of the phase comparator upon the detection of the slipping condition. Also described are circuits to implement the phase comparator and a transconductance compensation circuit for a filter, and methods of comparing phase and transconductance compensation.

Abstract: While generating a correction pulse (E) based on a clock signal (Xck1) input into one input terminal (6), a frequency and a phase of a differentiated pulse train (Data_Dif) input into the other input terminal (5) are compared with a frequency and a phase of the clock signal input into the one input terminal, then a leading phase instructing pulse (U4) and an incomplete lagging phase instructing pulse (D4a) are generated based on this compared result, then false pulses contained in the incomplete lagging phase instructing pulse (d4a) are removed by using the correction pulse (E) when the differentiated pulse train (Data_Dif) input into the other input terminal is in the tooth missing state, and then the precise leading phase instructing pulse (U4) and the precise lagging phase instructing pulse (D4) are output from two output terminals (7, 8).

Abstract: Modern fiber optic networks typically transfer data using encoding in which the clock is transmitted along with the data, for example in NRZ format. In order to use the clock to process the data, the clock signal must be extracted from the data signal. Because the data and clock may travel through different circuit paths they may have different propagation delays and a phase offset between the clock and data may result. Data and clock phase offsets are more problematical as data transmission speed increases. Furthermore the data/phase offset is typically not constant and may change with a variety of variables. To compensate for the changing offset, one or more variable delays are inserted in the phase detector circuitry. The timing of the variable delay is controlled by a bang-bang phase detector, such as an Alexander phase detector, which determines if the clock is leading, lagging, or in phase with the data.

Abstract: A method and apparatus for synthesizing high-frequency signals, such as wireless communication signals, includes a phase-locked loop (PLL) frequency synthesizer with a variable capacitance voltage controlled oscillator (VCO) that has a discretely variable capacitance in conjunction with a continuously variable capacitance. The discretely variable capacitance may provide coarse tuning adjustment of the variable capacitance to compensate for capacitor and inductor tolerances and to adjust the output frequency to be near the desired frequency output. The continuously variable capacitance may provide a fine tuning adjustment of the variable capacitance to focus the output frequency to match precisely the desired frequency output. During fine tuning adjustment, the PLL may be controlled by a plurality of analog control signals. The analog control signals may be derived by first generating a plurality of phase shifted signals from a divided version of the VCO output clock by using a shift register.

Abstract: The present invention provides delay locked loop circuits, phase detectors and methods for producing a delayed signal from a periodic input signal. An intermediate delay signal as well as an input signal and a delayed output signal are provided to a delay control circuit that controls the delay of a delay circuit based on a comparison of the input signal and output signal following a transition of the intermediate signal. The apparatus and methods of the present invention may thereby be able to distinguish between a case in which tTOTAL=T and tTOTAL=2T to reduce the potential for locking in a false state.

Abstract: The present invention provides a phase comparator provided in a phase locked loop circuit, the phase comparator converting a phase difference between first and second input signals into a current signal, wherein the phase comparator has: a lock detector for detecting locked and unlocked states of the phase locked loop circuit to generate a detected signal which indicates one of the locked and unlocked states; and a current source connected to the lock detector for receiving the detected signal from the lock detector and varying a supply current based on the detected signal, so that if the detected signal indicates the unlocked states, then the current source increases the supplying current.

Abstract: A digital phase detector utilizes a digital compartor and a plurality of delay elements. The comparator compares two signals and generates an output signal with a duration corresponding to the time delay between the arrival times of two signals. The output signal propagates through the plurality of delay elements. The number of delay elements that cover the duration of the output signal determine a time value for the duration of the output signal.

Abstract: The present invention provides a dual mode phase and frequency detector for use with a charge pump and a loop filter. The charge pump is adapted to adjust charging or discharging of the loop filter to adjust a VCO for generating a digital clock. The dual mode phase and frequency detector includes a phase and frequency detector and a first delay element. The phase and frequency detector is arranged to receive the VCO clock for tracking a reference clock signal. The phase and frequency detector generates control signals in response to the VCO clock and the reference clock signal. The control signals control charging or discharging of a loop filter in a DLL when the phase and frequency detector is operating in a phase and frequency detector mode. The first delay element is coupled to receive one of the control signals from the phase and frequency detector for generating an auxiliary control signal in response to the VCO clock.

Abstract: A phase detector circuit (100) operating at a high frequency includes a steering circuit (112) operating on frequency-divided versions of the phase detector signals. The phase detector (100) implements steering by adding dividers (108, 110) at both input ports to the steering circuit (112). This achieves the desired effect of reducing the operating frequency of the input signals to the steering circuit (112) to make operation possible at high frequencies of operation. The phase detector (100) also allows the steer circuit (112) to be turned off in steady state operation, this is accomplished by coupling only the steer outputs of the steering circuit (12) to the tuning line. The phase/frequency detect outputs are not coupled to the tuning line.

Abstract: A phase comparison of timing signals is made by combinational circuitry which receives the timing signals and a window signal, the window signal identifying edges of the timing signals to be compared. The comparison may result in a charge pumped output which can be fed back to control the phase of one of the timing signals. The phase comparator and charge pump circuit can be included in a multiplier circuitry in which the phase of an input signal is directly compared to the phase of an edge of the multiplied signal.

Abstract: A digital phase shift amplification and detection system and method for amplifying and detecting a phase shift. A signal is applied to a digital phase shift amplifier including a flip flop operated in the metastable region in which the applied signal transitions at a relatively close time to a trigger in the clock signal of the flip flop. The digital phase shift amplification and detection system and method amplifies any timing changes in the signal. The amplified signal is fed into a detection circuit configured to detect timing delays in the amplified signal. A signal is applied to a digital phase shift amplifier including a flip flop operated in the metastable region which amplifies any timing changes in the signal. The amplified signal is fed into a detection circuit configured to detect the amplified timing differences in the amplified signal as a result of a relatively smaller timing change in an input signal.

Abstract: An improved digital phase detector is provided for detecting and compensating for a cycle slip between a reference signal and a frequency source signal, the reference and frequency source signals each comprising pulses, each pulse defined by a leading edge and a trailing edge. The digital phase detector includes a detector circuit for detecting a cycle slip where two successive leading edges of one of the reference and frequency source signals are received before a leading edge of the other signal is received. An output circuit is operatively coupled to the detector circuit for developing a correction signal responsive to said detecting.

Abstract: A phase detector for a timing control loop provided in a signal sampling system to control taking samples by a sampler of input signals provided to a signal sampling system to result in a signal sample sequence output using a slope estimator and an error determiner with a phase error estimator combiner. The combiner output is provided to a summer directly and through a delay element to form phase error estimates.

Abstract: A three-state phase detector, including two latches and one NAND gate, is provided with two additional latches. To detect a phase difference between first and second input clock signals R and V, the phase detector alternates among three states responsive to a rising edge of the input R or V signal. Each of the two additional latches and an associated latch in the phase detector together constitute one shift register. When the phase detector gets back to its neutral state, the NAND gate generates a reset signal, thereby resetting all of these four latches. Two isolated pulse generators are further provided. Each of the pulse generators makes the pulse width of a frequency difference pulse signal, output from associated one of the additional latches, constant and then outputs the pulse signal with the constant width.

Abstract: A phase frequency detection circuit of a phase locked loop (PLL) for liquid crystal display which compares a phase between an external synchronous signal and an internal synchronous signal from the PLL to generate a phase difference detection signal, including: a dividing circuit for dividing the external synchronous signal and the horizontal synchronous signal; a phase difference detecting circuit for detecting the phase difference between the divided external synchronous signal and the divided horizontal synchronous signal from the dividing circuit; a phase discriminating circuit for discriminating whether the divided external synchronous signal is ahead of the divided horizontal synchronous signal and generating the phase discriminating signal; and a comparison device for receiving the phase difference detection signal from the phase difference detection circuit and the phase discriminating signal from the phase discriminating circuit to generate the phase frequency difference signal.

Abstract: The present invention provides a phase detector without dead zone, which can reduce clock jitter and provide higher tolerance for data random jitter. It can output a plurality of control signals (up,dn) through the function of a plurality of multi-phase clock signals to detect the transition edge of data signals. Therefore, the relation between the phase error &thgr;e and the voltage Vd of a phase-locked loop can be adjusted to be nearly linear dependent. In this way, the phase-locked loop in accordance with the present invention has no dead zone, clock jitter can be reduced and tolerance for data random jitter can be enhanced.

Abstract: By applying a modification considering a frequency difference to a phase error signal, phase lock is established in a short period of time even when there is a frequency difference. A jump detector detects a discontinuous jump of the phase error signal which occurs when there is a frequency difference, and a state transition is caused in a state storage device in accordance with the resulting detection signal. A holding device corrects the phase error signal in accordance with the state stored in the state storage device and outputs the thus corrected phase error signal as a frequency-phase error signal.

Abstract: Provided are a phase comparator (BBD) 10 for generating a pulse of a signal UP0 or DOWN0 depending on lead or lag of the falling edge of a clock recovered from DATA, relative to the edge of DATA, an overrun detector circuit 20 activating an overrun signal OVR while the circuit 20 detects that lead or lag of the falling edge of the clock exceeds &pgr;/2, a state latch circuit 30 latching a state of either a signal UP0 or DOWN0 being active before the signal OVR transits active, and a selection circuit 40 outputting the signals UP0 and DOWN0 as signals UP and DOWN while the signal OVR is inactive, and outputting the signals UP0 and DOWN0 as the signals DOWN and UP while the signal OVR is active.

Abstract: A circuit comprising a pump-up circuit and a pump-down circuit. The pump-up circuit may be configured to generate a pump-up signal in response to (i) a data signal and a clock signal. The pump-down circuit may be configured to generate a pump-down signal in response to (i) the data signal, (ii) the clock signal, and (iii) a quadrature of the clock signal.

Abstract: A phase comparator that is configured with a fewer number of gates in an ECL circuit configuration as compared to conventional phase comparator circuits. The phase comparator also operates with lower current consumption, and can achieve a suitable detection of small phase difference by substantially suppressing the influence of spike noises which may arise in the signals input to the phase comparator.

Abstract: A circuit monitor performance of an integrated circuit. The circuit includes a clock signal and a phase delay detection circuit. The clock signal is used by the integrated circuit to generate an output signal on an output pin of the integrated circuit. The phase delay detection circuit detects relative phase difference between the clock signal and the output signal on the output pin of the integrated circuit. The phase delay detection circuit includes a digital signal generator and an integrator. The digital signal generator is connected to an output pin of the integrated circuit. The digital signal generator generates a digital signal. Changes in phase delay between the output signal on the output pin of the integrated circuit and the clock signal used by the integrated circuit are encoded in a duty cycle of the digital signal generated by the digital signal generator. The integrator is connected to the digital signal generator and integrates the digital signal to produce an integrated signal.

Abstract: There is disclosed a phase detector which triggers on both rising and falling edges of an input pulse signal. This effectively doubles the frequency of the input signal. When the phase detector is used in a phase locked loop, the doubled frequency means that a lower division ratio can be used, thereby reducing any noise contribution introduced thereby.

Abstract: A phase comparator compares the phases of first and second signals with each other. The phase comparator has a first control circuit, a second control circuit, and a phase comparator unit. The first control circuit divides the frequency of the first signal by n in response to a third signal where n is an integer equal to or larger than 2. The second control circuit divides the frequency of the second signal by n in response to the third signal. The phase comparator unit compares the phases of signals provided by the first and second control circuits with each other. The phase comparator unit is capable of correctly comparing the phases of even high-speed signals with each other, and therefore, is applicable to a DLL circuit that operates on high-speed clock signals.

Abstract: An apparatus for and method of reducing transistor body effect when detecting and correcting a phase error between clock signals using delay-locked and phase-locked loop circuits. The clock signals are provided to an equal number of circuit elements in cross-coupled XOR circuits. The circuit includes a transconductance circuit having at least two PMOS transistors with their substrates directly connected to their sources.

Abstract: A phase detector and a method for detecting phase difference between two high frequency signals, the phase detector is adapted to receive a reference signal REF, a high frequency signal ICOS, and a signal FD synchronized to ICOS. REF, ICOS and FD have opposite edges. The phase detector comprising of: An asynchronous phase detector circuit, for providing an asynchronous control signal CTP, for representing a time interval between a time of occurrence of an edge of REF and the time of occurrence of a corresponding edge of ICOS. A synchronous phase detector circuit, for providing an synchronous control signal TC, for representing a time interval between a time of the occurrence of the corresponding edge of ICOS and the time of occurrence of a corresponding edge of FD.A combing circuit, for receiving TC and CTP and providing an error signal ERS, representing the phase difference between REF and FD.

Abstract: An output of a flip flop (21) at a first stage is connected to a D-input of a flip flop (22) at a second stage, and an inverted-output of the flip flop (21) is connected to a D-input of a flip flop (23) at a third stage. A reference clock BCK is supplied to the D-input of the flip flop (21), and an oscillation clock OCK is inputted to each T-input of the respective flip flops (21) to (23). An XOR of the reference clock BCK and an output signal Q1 of the flip flop (21), and a logical product of an output signal Q2 of the flip flop (22) and an output signal Q3 of the flip flop (23) are used as a first comparison output PDU and a second comparison output PDD, respectively. With this arrangement, phase comparison can be achieved using a clock of any duty ratio.

Abstract: A phase detector for measuring phase differences between K input signals is provided. The phase detector includes a counter, K first registers and a first subtractor. Each first register receives the counter signal of the counter and a respective input signal for updating a counter value in response to timing information on the input signal. The first subtractor receives the counter values to generate phase difference representing values. A frequency detector is also provided. The first subtractor is substituted by a second subtractor and K second registers are included. Each second register is connected to a respective first register. Each second register receives the counter value of its first register and the same input signal as that of its first register for backing-up the counter value as a back-up counter value in response to the timing information on the input signal.

Abstract: To form a means preventing a logic circuit from outputting wrong data at uncontrolled, unstable state of power turn-on in a control circuit. The control circuit has two logic circuits therein and takes negative OR or negative AND of output thereof. A first input terminal is connected to an input of an inverter circuit and a second logic circuit; the output of the inverter circuit is connected to the input of the first logic circuit; a second input terminal is connected to the first logic circuit and the second logic circuit; outputs of the first logic circuit and the second logic circuit are connected to inputs of a gate circuit; the output of the gate circuit is connected to a output terminal; and the first logic circuit and the second logic circuit output the opposite level to each other, positive and negative.

Abstract: The invention provides an improved method and apparatus for detecting the phase difference between a digital data signal and a clock signal. By ensuring that no pulse in the output phase signal is narrow enough to introduce a non-linearity, the present invention avoids a source of non-linearity exhibited in existing phase detectors.In addition, by ensuring that critical timing paths through the circuit contain similar circuit blocks, with similar propagation delays, relative time relationships are preserved from clock and data inputs to XOR inputs. The circuit is therefore largely insensitive to changes in the characteristics of the components so long as they all move together, as they would in an integrated circuit implementation.

Abstract: The synthesis of high-frequency signals, such as wireless communication signals, includes a phase-locked loop (PLL) frequency synthesizer with a variable capacitance voltage controlled oscillator (VCO) that has a discretely variable capacitance in conjunction with a continuously variable capacitance. The discretely variable capacitance may provide coarse tuning adjustment of the variable capacitance to compensate for capacitor and inductor tolerances and to adjust the output frequency to be near the desired frequency output. The continuously variable capacitance may provide a fine tuning adjustment of the variable capacitance to focus the output frequency to match precisely the desired frequency output. During fine tuning adjustment, the PLL may be controlled by a plurality of analog control signals. The analog control signals may be derived by first generating a plurality of phase shifted signals from a divided version of the VCO output clock by using a shift register.

Abstract: A PLL system (10) includes a PFD (24) that receives a reference clock signal (REF CLK) and a feedback clock signal (FBK CLK). The PFD (24) generates an analog signal (TUNE) based on the phase and frequency relationship of the reference and feedback clock signals. The PFD (24) also generates a clock signal based on two PI phase slips for clocking a counter (70). The analog signal is compared against an upper and lower reference voltage in a threshold detect circuit (34) and the signals UP and DOWN supplied to the counter (70). The counter (70) provides a count value that controls the resonant frequency generated by a tank circuit (73). The tuning range of an oscillator (18) is extended by changing the capacitance of the tank circuit (73).

Abstract: A digital phase comparator comprises a first signal input (VCO) and second signal input (REF) as well as a first output (UP+) and second output (DOWN+). It is arranged so as to produce an output pulse (503, 504) to the first output and second output per each of the cycles of the periodic signals (501, 502) brought to the first signal input and second signal input. The duration of the output pulse produced to the first output is longer than the duration of the output pulse produced to the second output when the phase of the periodic signal brought to the first signal input is lagging with respect to the phase of the periodic signal brought to the second signal input. Correspondingly, the duration of the output pulse produced to the first output is shorter than the duration of the output pulse produced to the second output when the phase of the periodic signal brought to the first signal input is leading with respect to the phase of the periodic signal brought to the second signal input.