Abstract: A clock divider circuit including a clock input, a clock selection input, a divider stage and a toggle stage is provided. The clock divider circuit provides an output clock based on a clock input received at the clock input. The clock selection input is coupled to the divider stage, and the divider stage is coupled to the toggle stage. A clock divide setting is updated at the clock selection input synchronously to an operation of the divider stage. In one implementation, for example, the clock divider setting is updated seamlessly. A method of transitioning an output clock signal is also provided.

Abstract: In one or more embodiments, a programmable clock divider (PCD) can receive an input clock signal and a programmable number, and the PCD can produce a divided clock signal based on the programmable number. First and second circuits can compare first and second numbers, respectively, with a count value from a counter to generate first and second signals, respectively. A multiplexer can receive the first and second signals at inputs and can receive the clock signal at a selection input. The multiplexer can output an output signal, as a divided clock signal, based on the clock signal, the first signal, and the second signal, where the output signal transitions from a first value to a second value on at least one of a first edge of the first clock signal to output the first signal and a second edge of the first clock signal to output the second signal.

Abstract: There is provided a true single phase logic clock divider that is configured to selectively divide a clock signal by increments of two, three, four, or six. Because the true single phase logic clock divider is based on true single phase logic instead of static logic, the true single phase logic clock divider is able to reliably divide clock signals that could not reliably be divided by clock dividers based on static logic gates. The true single phase logic clock divider is capable of reliably operating at frequencies of greater than or equal to two gigahertz.

Abstract: A clock system includes a phase locked loop, a phase divider, and a control module. The phase locked loop (PLL) produces a plurality of phase-offset output oscillations. The phase divider generates a clock signal from one or more of the plurality of phase-offset output oscillations based on a phase divider control signal. The control module generates the phase divider control signal based on a desired setting for the clock signal.

Abstract: A frequency divider can include at least one input device receiving an input signal, the at least one input device converting the input signal to a current signal; a driver stage with at least two drivers, the at least two drivers receiving the current signal from the at least one input device; a latch stage with at least two latches receiving output signals from the driver stage, the latch stage amplifying the output signals from the driver stage in proportion to an imbalance on the driver stage; and a feedback loop feeding back latch stage output signals to the driver stage. The driver stage and the latch stage can divide the input signal such that the current signal has a frequency of a multiple of the divided signal, and the frequency divider can also include at least one output device to convert the divided signal to a divided voltage signal.

Abstract: A semiconductor device for applying an auto clock alignment training mode to reduce the time required for a clock alignment training operation. The semiconductor device adjusts the entry time of the auto clock alignment training mode to prevent the clock alignment training operation from malfunctioning. The semiconductor device includes a clock division block configured to divide a data clock to generate a data division clock, a phase multiplex block configured to generate a plurality of multiple data division clocks in response to the data division clock, a logic level control block configured to set a period, in which a division control signal is changeable, depending on the data division clock, and a first phase detection block configured to detect a phase of a system clock on the basis of the multiple data division clocks in the period, and to generate the division control signal corresponding to a detection result.

Abstract: A semiconductor device includes a clock input block to receive a system clock and a data clock, a clock frequency dividing block to generate a plurality of multi-phase data frequency division clocks each of which has the phase difference of a predetermined size by dividing a frequency of the data clock and to determine whether or not phases of the plurality of multi-phase data frequency division clocks are reversed in response to a frequency division control signal, and a first phase detecting block to detect a phase of the system clock based on a phase of a first selected clock that is predetermined among the plurality of multi-phase data frequency division clocks and to is determine a logic level of the frequency division control signal in response to the detected result.

Abstract: A multimode millimeter-wave frequency divider circuit with multiple selectable frequency dividing modes is proposed, which is designed for integration with a millimeter wave (MMW) circuit system, such as a phase-locked loop (PLL) circuit, for providing multimode frequency dividing functions. In actual application, the millimeter wave frequency divider circuit of multi frequency dividing mode provides at least three frequency dividing operational modes, including modes of dividing two, dividing 3 and dividing four. In practice, the millimeter wave frequency divider circuit of multi frequency divider mode may be integrated with a millimeter wave phase-locked circuit to provide a frequency synthetic function having multi frequency sections, such as including 38 GHZ, 60 GHZ and 77 GHZ, and may use reduced circuit layout surfaces and operational power.

Abstract: A phase locked loop (PLL) is provided. In one implementation, the PLL includes a multiphase voltage controlled oscillator (VCO) operable to generate an output signal containing one or more phase signals, a programmable divider operable to divide a frequency of the output signal of the multiphase VCO to produce a divided frequency output signal, and a fractional divider to fractionally divide an input phase signal. The fractional divider can include an integer divider operable to receive the input phase signal and divide the input phase signal in accordance with an integer divisor to produce a divided signal as an input to the multiphase VCO, and a phase interpolator operable to select a phase signal from among the one or more phase signals output by the multiphase VCO, to produce an interpolated output signal having a desired frequency resolution.

Abstract: A system and method of loading a programmable counter includes storing a first digital divide value in a register. The first digital divide value is then loaded from the register to a programmable counter. The method further includes writing a second digital divide value to the register at a time responsive to a time remaining to complete a counting cycle of the programmable counter.

Abstract: A clock signal dividing circuit in which a dividing ratio is regulated by N/M (M and N are positive integers and satisfy M>N) includes: a variable delay circuit which gives a predetermined delay amount based on a control value to an input clock signal CKI to output an output clock signal CKO; and a variable delay control circuit which cumulatively adds values obtained by subtracting N from M every cycle of the input clock signal CKI, when the addition result is N or more, performs a calculation which subtracts N from the addition result to obtain a calculation result K, and calculates, to a maximum delay amount in the variable delay circuit corresponding to one cycle of the input clock signal CKI, a control value corresponding to a delay amount of K/N of the maximum delay amount to give the control value to the variable delay circuit.

Abstract: A frequency synthesizer includes first and second frequency dividers for receiving and frequency-dividing a signal generated by a voltage-controlled oscillator, a frequency mixer for mixing output signals of the first and second frequency dividers, and a third frequency divider for receiving and frequency-dividing a signal having one frequency of two frequencies that are output by the frequency mixer. The first, second third and frequency dividers and the frequency mixer are provided in a feedback loop within a PLL circuit between the voltage-controlled oscillator and the phase comparator. The phase comparator has a first input terminal to which a signal to which a signal that is output by the third frequency divider is input and a second input terminal to which a reference clock signal that is output by a reference signal generator is input. A loop filter supplies the voltage-controlled oscillator with a voltage that is based upon result of the phase comparison by a phase comparator.

Abstract: A divider circuit for dividing the frequency of a multi-phase clock signal, which can ensure a sufficient data latch time even if the multi-phase clock signal has a high frequency, includes a main latch circuit which generates an inverted data signal using, for example, two of eight clock signals of an eight-phase clock signal, and a sub-latch circuit which uses the eight clock signals as a trigger to receive the inverted data signal as a common data signal.

Abstract: The phase locked loop has a phase-frequency detector (PFD), a loop filter (LF), a voltage controlled oscillator (VCO), and a 3-stage frequency divider. The PFD receives a reference signal and a feedback signal to determine phase and frequency errors. The LF), coupled to the phase-frequency detector, filters the phase and frequency errors to generate a control voltage. The VCO, coupled to the loop filter, generates a VCO output signal according to the control voltage. The 3-stage frequency divider, coupled to the voltage controlled oscillator, divides the frequency of the VCO output signal 3 times to generate the feedback signal. The 3-stage frequency divider comprises three cascaded frequency dividers with different rangers of operating frequencies.

Abstract: This disclosure relates to a divide-by-N frequency divider system and frequency dividing method. The system includes a ring oscillator having M stages, where M is an integer, and a zero mean current component coupled to one or more of the stages to provide a zero mean current flow path.

Abstract: A first frequency dividing circuit and a second frequency dividing circuit are provided, and these circuits frequency-divide two-phase external clocks injected from an external part, to output four-phase clocks with phase guarantee. Each of the frequency dividing circuits includes a mixer, an adding circuit, and a phase circuit. The first frequency dividing circuit and the second frequency dividing circuit are coupled in loop shape via a first coupling circuit and a second coupling circuit. The first coupling circuit receives a first output signal of the first frequency dividing circuit to output a second external input signal to the second frequency dividing circuit, and the second coupling circuit receives a second output signal of the second frequency dividing circuit to output a first external input signal to the first frequency dividing circuit, and a clock frequency dividing circuit with a high loop gain and a wide lock range can be realized.

Abstract: A clock switch circuit includes a frequency divide circuit which divides a frequency of a basic clock to generate a plurality of frequency-divided clocks, an output select signal generation circuit which outputs an output select signal according to a clock select signal, and an output select circuit which switches a clock to be output according to the output select signal, in which the frequency divide circuit outputs a plurality of frequency-divided count values indicating the number of clocks of the basic clock from start of one cycle of each of the frequency-divided clocks, and the output select signal generation circuit switches a value of the output select signal at timings at which start timings of cycles of frequency-divided clocks before and after switch operation are matched based on a frequency-divided count value corresponding to a current selection clock among the plurality of frequency-divided count values.

Abstract: A distributed charge pump system uses a delay element and frequency dividers to generate out of phase pump clock signals that drive different charge pumps, to offset peak current clock edges for each charge pump and thereby reduce overall peak power. Clock signal division and phase offset may be extended to multiple levels for further smoothing of the pump clock signal transitions. A dual frequency divider may be used which receives the clock signal and its complement, and generates two divided signals that are 90° out of phase. In an illustrative embodiment the clock generator comprises a variable-frequency clock source, and a voltage regulator senses an output voltage of the charge pumps, generates a reference voltage based on a currently selected frequency of the variable-frequency clock source, and temporarily disables the charge pumps (by turning off local pump clocks) when the output voltage is greater than the reference voltage.

Abstract: A divider of an input multiphase signal by a given division factor so as to obtain an output multiphase signal, the divider having a circuit adapted to divide a first signal component of an input multiphase signal by an given division factor to obtain a first component of a output multiphase signal, and a plurality of N?1 devices including a first device adapted to sample the first component with a component of the input multiphase signal to obtain the component of the output multiphase signal corresponding to the one component of the input multiphase signal. Every other device of the plurality of N?1 devices is adapted to sample the component of the output multiphase signal of the preceding device with another component of the input multiphase signal, phase shifted by a further constant factor to obtain the corresponding component of the output multiphase signal.

Abstract: A frequency divider includes a transmission gate, a first inverter, a first switch circuit, a second switch circuit, and a second inverter. The transmission gate transmits a clock signal according to an inverted enable signal. The first inverter inverts the clock signal outputted from the transmission gate. The first switch circuit generates a first control signal according to the inverted clock signal and an output signal of the frequency divider. The second switch circuit generates a second control signal according to the clock signal, the inverted clock signal, and the first control signal. The second inverter inverts the second control signal to generate the output signal. The frequency of the clock signal is a multiple of the frequency of the output signal.

Abstract: A local oscillator includes a programmable frequency divider coupled to the output of a VCO. The frequency divider can be set to frequency divide by three. Regardless of the divisor, the frequency divider outputs quadrature signals (I, Q) that differ from each other in phase by ninety degrees. To divide by three, the frequency divider includes a divide-by-three frequency divider. The divide-by-three frequency divider includes a divide-by-three circuit, a delay circuit, and a feedback circuit. The divide-by-three circuit frequency divides a signal from the VCO and generates therefrom three signals C, A? and B that differ from each other in phase by one hundred twenty degrees. The delay circuit delays signal A? to generate a delayed version A of the signal A?. The feedback circuit controls the delay circuit such that the delayed version A (I) is ninety degrees out of phase with respect to the signal C (Q).

Abstract: A frequency divider including at least one frequency divider cell having an adjustable circuit configuration which may be selected adaptively according to properties of an oscillator signal to be frequency-divided in the frequency divider. Accordingly, the circuit configuration of the frequency divider may be changed on the fly during the operation.

Abstract: A frequency dividing section is made up of a frequency divider for dividing output of a local oscillator, a frequency divider for dividing output of an in-phase local oscillation signal of the frequency divider, and a dummy circuit connected to the output terminal of a quadrature local oscillation signal of the frequency divider. At the first frequency band operation time, output of the frequency divider is used for modulation and demodulation and at the second frequency band operation time, output of the frequency divider is used for modulation and demodulation. Although the frequency divider is shared between the first and second frequency bands, the dummy circuit is made the same circuit as an input amplifier of the frequency divider at the first frequency band operation time, so that the phase difference between the in-phase local oscillation signal and the quadrature local oscillation signal output by the frequency divider can be kept.

Abstract: A frequency divider using a clock source with a plurality of phase signals of a multi-phase oscillator. In one version, the divider includes a plurality of spot-moving stages that are connected to form a ring. Spot-moving stages are stages that advance a one or a zero, while clearing the previous stage. Depending on the number of stages and the number of phases of the clock to advance a spot through all of the stages, a divider ratio is determined. In another embodiment, a plurality of latch elements is provided with a divided input and each is re-clocked with the phases of a multi-phase oscillator. The outputs of the latch elements are combined in a capacitor array to create the output waveform. An interpolator useful in conjunction with a frequency divider is also disclosed. When the interpolator is placed in the feedback path of a PLL, a fractional frequency multiplier/divider results.

Abstract: Fractional frequency division is performed by sequentially selecting phase signals for division, where transitioning from a previous phase signal to a next phase signal for division occurs in response to not only the frequency-divided previous phase signal but also a second one of the phase signals. A phase transition that is triggered at least in part in response to a second phase signal having a phase that is greater (with respect to the phase signal sequence) than the phase of the next phase signal can aid minimization of signal glitches. The first frequency-divided signal can be further divided to produce a second frequency-divided signal having a 50-percent duty cycle.

Abstract: A frequency divider includes a transmission gate, a first inverter, a first switch circuit, a second switch circuit, and a second inverter. The transmission gate transmits a clock signal according to an inverted enable signal. The first inverter inverts the clock signal outputted from the transmission gate. The first switch circuit generates a first control signal according to the inverted clock signal and an output signal of the frequency divider. The second switch circuit generates a second control signal according to the clock signal, the inverted clock signal, and the first control signal. The second inverter inverts the second control signal to generate the output signal. The frequency of the clock signal is a multiple of the frequency of the output signal.

Abstract: A circuit for deriving an output clock signal from an input clock signal, the output clock signal having a frequency which is 1/Nth of the frequency of the input clock signal, where N is an odd number. The circuit comprises a plurality of latches configured as a latch ring, the latches being arranged in successive pairs, each pair of latches comprising a first latch that switches on one of the rising or falling edge of the input clock signal, and a second latch that switches on the other of the rising or falling edge of the input clock signal. An RS flip flop is coupled to receive at one of its set and reset inputs an output from the latch ring that is switched on a rising edge, and at the other of the set and reset inputs an output from the latch ring that is switched on a falling edge. Said output clock signal is provided at an output of the RS flip flop.

Abstract: Each of n level shifters (LS0 to LS7) includes an NMOS transistor (Mn1) for receiving any one of n clock signals (P0 to P7) and a PMOS transistor (Mp1) for receiving an output signal from another level shifter. An output signal given to the PMOS transistor (Mp1) included in each of the level shifters (LS0 to LS7) is an output signal of the level shifter which receives the clock signal whose phase delay amount with respect to the clock signal given to the NMOS transistor (Mn1) included in that level shifter is a phase amount X (0°<X<180°). The phase amounts X of the n level shifters (LS0 to LS7) are equal to each other.

Abstract: An embodiment of this invention combines feed-forward and feedback frequency division circuits in a such a way, to provide greater flexibility in choosing the non-integer division ratios at the output, with little added complexity. Alternate embodiments include additional divider(s) in signal or feedback paths providing additional flexibility and design simplification. An embodiment uses in-phase/quadrature signals to select the desired modes at feedback-path and signal-path mixers. Various alternatives are also described.

Abstract: In a method for dividing a frequency of a clock signal, a first frequency divided signal is generated based on a clock signal. Rising edges in the first frequency divided signal are detected. Alternatively, falling edges in the first frequency divided signal are detected. An edge detection signal that includes a pulse for each detected edge is generated. A second frequency divided signal is generated based on the edge detection signal.

Abstract: A frequency divider includes a prescaler and multiple modulus dividers commonly coupled to the prescaler. The prescaler generates intermediate frequency signals having a same phase difference with respect to one another in response to an oscillation frequency signal. The prescaler operates at a first frequency. The modulus dividers respectively divide the intermediate frequency signals with respective ratio to provide a plurality of division frequency signals in response to a control signal. The modulus dividers operate at a second frequency less than the first frequency.

Abstract: A clock dividing circuit includes a control logic unit and a flip-flop. The control logic unit outputs an enable signal and a data signal according to a clock signal and a division ratio. The flip-flop outputs a divided clock signal based on the clock signal, the enable signal and the data signal. The clock signal can be directly outputted as the divided clock signal through the flip-flop.

Abstract: A phase shifter according to an embodiment of the present invention includes: an AC component amplifying unit; and a dividing circuit. The AC component amplifying unit has positive gain slope characteristics and deforms a waveform of an input differential clock signal to output the deformed differential clock signal. The dividing circuit includes a T-flipflop having two D latches connected in series and receives the deformed differential clock signal defoemed by the AC component amplifying unit to generate at least two output signals having a phase difference of 90 degrees with a frequency of ½ of the deformed differential clock signal.

Abstract: An injection-locked frequency divider for dividing a frequency of an injection signal and obtaining a frequency divided signal is provided. The injection-locked frequency divider includes a signal injection unit and an oscillator. The signal injection unit includes a first input terminal and a second input terminal for receiving the injection signal. The received injection signal exhibits a phase difference of 180° between the first input terminal and the second input terminal. The oscillator includes an inductor unit and a variable capacitance unit. The injection-locked frequency divider is featured with a wide injection locking range, and can be realized with a low operation voltage, and therefore can be conveniently used in different kinds of hybrid ICs.

Abstract: A frequency dividing circuit performs a frequency dividing operation on N input clock signals to obtain N output clock signals, wherein N is a natural number greater than 1. The frequency dividing circuit includes a frequency divider and a flip-flop. The frequency divider samples an initial signal according to a first input clock signal of the N input clock signals to accordingly generate a first output clock signal of the N output clock signals. The initial signal corresponds with an inverse signal of the first output clock signal. The flip-flop samples the first output clock signal to accordingly generate a second output clock signal of the N output clock signals according to a second input clock signal of the N input clock signals.

Abstract: A system timer including a divider unit configured to fractionally divide a first clock signal and output a second clock signal having an asymmetric duty ratio and an interrupt generation unit configured to count a cycle of the second clock signal and output an interrupt signal according to the count.

Abstract: A system and method are provided for controlling the duty cycle and frequency of a digitally generated clock. The method accepts a first clock signal having a fixed first frequency. A frequency control word with a first pattern is loaded into a first plurality of serially-connected registers. A duty cycle control word with a second pattern is loaded into a second plurality of serially-connected registers. A register clock signal is generated in response to the first clock and the first pattern. Then, a digital clock signal is generated having a frequency and duty cycle responsive to the register clock signal and the second pattern.

Abstract: A frequency divider circuit includes: a shift register capable of storing at least n-bit data configured to shift an input signal sequentially in synchronization with a clock signal; a pulse generating circuit configured to change the input signal into a pulse form in response to a change in logic level of an output signal from a stage of the shift register among n-bit output signals from the shift register, the stage corresponding to a bit resulting from shifting of the input signal by n bits; and a frequency dividing signal generating circuit configured to generate a frequency dividing signal whose logic level is inverted in response to a change in logic level of an output signal from any one stage of the shift register or logic level of the input signal, in order to divide the clock signal in frequency by a dividing ratio corresponding to the n bits.

Abstract: A digital time base generator and method for providing a first clock signal and a second clock signal in which a base clock signal having a base frequency is generated to provide two clock signals of slightly different frequencies with defined time or phase delay. Here, the base frequency is divided by a first integer to produce a first auxiliary signal, the frequency of the first auxiliary signal is multiplied by a factor to obtain the first clock signal, the base frequency is further divided by a second integer to produce a second auxiliary signal, and the frequency of the second auxiliary signal is multiplied by the factor to obtain the second clock signal.

Abstract: The present invention provides for a self-correcting state circuit. A first flip flop is configured to receive a clock input and a first data input, and to generate a first output in response to the clock input and the first data input. A second flip flop is coupled to the first flip flop and configured to receive the clock input and to receive the first output as a second data input, and to generate a second output in response to the clock input and the first output. A first correction circuit is coupled to the second flip flop and configured to generate a corrected output. A third flip flop is coupled to the first correction circuit and configured to receive the clock input and to receive the corrected output as a third data input, and to generate a third output in response to the clock input and the third data input.

Abstract: A pulse width modulation circuit capable of linearly adjusting duty cycle with voltage, which comprises an input voltage source for generating an input voltage, a regulator for generating a regulated voltage, a first voltage-dividing unit for providing a first divided voltage, a second voltage-dividing unit for providing a second divided voltage, a third voltage-dividing unit for providing a third divided voltage, a voltage adder for adding the first divided voltage and the third divided voltage for generating a high level voltage, a waveform generator for generating an oscillating signal according to the high level voltage and the third divided voltage, and a comparator having a first input terminal coupled to the second voltage-dividing unit, a second terminal coupled to the waveform generator, and an output terminal for comparing the second divided voltage with the oscillating signal to output a pulse width modulation signal through the output terminal.

Abstract: Digital divider for low voltage LOGEN. LOGEN is a local oscillator generator. One implementation presented herein provides for a pseudo-complementary metal-oxide-semiconductor (CMOS), in that, it is not a true CMOS type circuitry that has no DC current dissipation, but nevertheless does operate well at relatively high frequencies and relatively low power supply voltage levels. Appropriately placed p-channel metal oxide semiconductor field-effect transistors (P-MOSFETs) and n-channel MOSFETs (e.g., N-MOSFETs) are employed to provide for an all digital divider circuitry. In some embodiments, four active circuitry element levels are stacked between a power supply voltage and ground voltage level. In other embodiments, three active circuitry element levels are stacked between a power supply voltage and ground voltage level. The three active circuitry element levels embodiment provides for a greater area savings (e.g.

Abstract: A frequency divider is disclosed herein. The frequency divider includes a first latch circuit and a second latch circuit coupled to the first latch circuit. Each of the first latch circuit and the second latch circuit includes a first level for generating a source current, a second level for receiving a pair of input signals and for generating a pair of output signals, and a third level for receiving the source current and a pair of clock signals. The second level is coupled between the first level and the third level. The first level includes a first transistor having a source terminal and a substrate both coupled to a source voltage. The third level includes a plurality of transistors controlled by the pair of clock signals. Each transistor in the third level has a source terminal and a substrate both coupled to ground.

Abstract: A frequency divider including a first frequency-dividing unit, a second frequency-dividing unit, a selecting unit, and a counting unit is provided. The first frequency-dividing unit receives an input signal and divides a frequency of the input signal for outputting a plurality of phase signals, wherein phases of the phase signals are mutually different. The selecting unit is connected to the first frequency-dividing unit for selecting one of the phase signals according to a control signal, so as to output an inner signal. The second frequency-dividing unit is coupled to the selecting unit for dividing a frequency of the inner signal to serve an output signal. The counting unit is coupled to the selecting unit for counting the inner signal and outputting a counting result as the control signal. Therefore, the output signal with about 50% duty cycle can be provided.

Abstract: A frequency divider comprising, a first latch circuit and a second latch circuit, the second latch circuit being crossed-coupled to the first latch circuit. Each latch comprises a respective sense amplifier coupled to a respective latch. The sense amplifiers comprise a first clock input for receiving a first clock signal. The latches comprise a second clock input for receiving a second clock signal having a second frequency, the second frequency being substantially double the first frequency.

Abstract: A method and a frequency dividing circuit (1) for dividing a frequency of an input clock signal (CLKin) by an odd number to generate an output clock signal (CLKout) with a lower frequency comprising at least two serially connected edge triggered latches clocked by said input clock signal (CLKin), wherein a last edge triggered latch of said serially connected edge triggered latches (4) inverts a triggering direction of a first edge triggered latch (4A) of said serially connected edge triggered latches (4).

Abstract: Techniques for scaling and switching clocks in a glitch-free manner are provided. For example, in one aspect of the present invention, a technique for switching a frequency associated with a master clock includes the following steps/operations. Two phase clocks are generated from a master clock, wherein the two phase clocks do not transition at substantially the same time. Then, one of the two phase clocks is used to create multiple frequencies by dividing the one phase clock, and the other phase clock is used to switch between the multiple frequencies of the one phase clock. Further, one of the two phase clocks may be in phase with the master clock and the other of the two phase clocks may be 180 degrees out of phase with the master clock such that they do not transition at the same time. Also, the two phase clocks may be non-overlapping.

Abstract: Divider circuitry for a phase-locked loop frequency synthesizer, the divider circuitry comprising a main divider configured to divide an input signal received from a feedback path of the phase-locked loop frequency synthesizer by a division ratio selected from a pair of dual modulus division ratios in accordance with a dual modulus selection signal; and an auxiliary divider comprising a shift register clocked by an output signal of the main divider, the shift register comprising a parallel input configured to receive parallel input data in the form of a fraction selection signal at the start of a cycle, and a serial output connected to a control input of the main divider, the auxiliary divider being configured to produce serial output data, each bit of which serves as a said dual modulus selection signal to cause the main divider to operate using one or the other of the pair of dual modulus main division ratios; the auxiliary divider being configured to produce a pulse once per cycle of the shift register

Abstract: A phase locked loop (PLL) based frequency translator provides a divider augmented with a sigma delta modulator (SDM) in a reference path. The PLL is configured as an all digital PLL and includes a bang-bang phase frequency detector, digital loop filter, and digitally-controlled oscillator. The frequency translator is located in either the reference clock path for division or the PLL feedback loop path for multiplication. The SDM produces a predictable noise characteristic set with known stochastic properties which can be used to smooth any discontinuity in the bang-bang phase frequency detector. The predictable noise of the SDM will produce a dithering delay that eliminates any hard discontinuities. This allows for a bang-bang phase frequency detector based digital PLL.

Abstract: The dual-modulus prescaler circuit (1) is devised to operate at a very high frequency. This circuit includes an assembly formed of two dynamic D-type flip flops (12, 13), and two NAND logic gates (15, 16) arranged in negative feedback between the two flip flops. The two flip flops are clocked by an input clock signal (CK) to supply a divided output signal (OUT) whose frequency matches the input clock frequency divided by 2 or by 3 as a function of a division mode selection signal (divb) applied to the input of the first NAND logic gate (15). One non-inverted output of the second flip flop is connected to one input of the first flip flop (12). The first dynamic flip flop includes three active branches and supplies a single inverted output signal. A third flip flop (14) with three active branches receives an inverted mode selection signal (div) at input in order to supply the mode selection signal to the inverted output thereof, clocked by the non-inverted output signal of the second flip flop.