117 results about "Spread spectrum clock generator" patented technology

The spread spectrum clock generator (SSCG) includes a phase comparator detecting phase difference between input clock and feedback clock; a charge pump supplying current depending on the phase difference; a loop filter converting the current to smoothed voltage; a voltage controlled oscillator generating a spread spectrum clock signal depending on the smoothed voltage; and a modulation signal generator generating modulation signal having amplitude depending on a modulation width set value. The SSCG further includes a modulation width detector detecting modulation width of the spread spectrum clock signal while comparing the modulation width with a modulation width target value to update the modulation width set value to narrow difference between the detected modulation width and the modulation width target value, followed by feeding back the updated modulation width set value to the modulation signal generator.

A clock recovery circuit and a method for reducing electromagnetic emission (EMI) and increasing an attainable clock frequency includes a spread spectrum clock (SSC) generator that receives an input clock signal and generates a frequency-modulated clock signal, and a zero-delay buffer circuit that receives and buffers said modulated clock frequency signed to generated an output clock signal. The frequency-modulated clock signal and the output clock signal are phase-aligned such that there is no phase difference between the output clock signal and the modulated frequency clock signal. The clock recovery circuit also includes a delay-locked loop (DLL) circuit that reduces related art jitter and skew characteristics, and a phase detector circuit that eliminates phase ambiguity problems of a related art phase detector.

A spread spectrum clock generator comprises a conventional closed-loop VCO and an open-loop VCO where both are coupled to the same point of the PLL. Both VCOs comprise a V-to-I converter followed by a current-controlled oscillator and are identical in design but only the open-loop VCO receives the modulation current to generate the spread spectrum clock signal. The open-loop ICO is part of the spread spectrum generator and in one embodiment of the invention receives feedback current signals representing the modulation method and modulation ratio. This ensures that the modulated clock output tracks the PLL output frequency. In a second embodiment the closed-loop VCO receives from the spread spectrum generator the feedback current signal representing the modulation method (center / down spread) while the open-loop VCO receives the feedback signal representing the modulation ratio.

The present invention provides a spread spectrum clock generator that is capable of preventing phase jumps and jitters and suppressing the occurrence of Electro Magnetic Interference components and that can easily be applied to large scale integrated circuits. The spread spectrum clock generator can be configured with a filter, quantizer, fractional divider, and other elements. Also, this clock generator circuitry can be configured by combination of a delta-sigma ΔΣ quantizer and factional divider so that sine wave modulation and random number modulation can be realized. Thereby, control with digital values can be performed. This clock generator prevents precipitous phase variations in the output high frequency clock and makes fine phase control possible. Consequently, EMI reduction by 20-30 dB can be expected.

A semiconductor device, a spread spectrum clock generator and method thereof are provided. The example semiconductor device may include a frequency dividing unit receiving an output signal, generating a first feedback signal and a second feedback signal by dividing a frequency of the received output signal, and a phase offset unit outputting the output signal having a predetermined or desired phase difference with a reference signal in response to the second feedback signal, wherein the second feedback signal having a higher frequency than the first feedback signal. The example spread spectrum clock generator may include a plurality of frequency dividers which are connected in series and a selector selecting and outputting one of a plurality of output signals, each of the plurality of output signals having a different phase difference with respect to a reference signal, in response to at least one output from one or more of the plurality of frequency dividers. The example method may include receiving a reference signal with a first frequency, generating a feedback signal having a second frequency, the second frequency higher than the first frequency and outputting at least one of a sequentially selected set of output signals in response to the generated feedback signal.

A spread spectrum clock generator (SSCG) control and inspection circuit provides a system and method for inspecting and controlling an external SSCG, and for verifying the modulation profile waveform of an external SSCG. An electronic circuit is included that can check for the presence of an optimal SSCG modulation profile in product subsystems, and in attached modular systems, including electronic plug-in features such as internal network adapters and cartridges. In one mode of the invention, an electronic circuit ensures continued radiated emissions compliance for field replaceable units or consumable parts within a product, such as a printer, a scanner, or a combination (or all-in-one) printer / scanner. In another mode of the invention, an electronic circuit may also act as a secondary security device for consumable products, such as toner cartridges or ink jet cartridges. In yet another mode of the invention, an electronic circuit may also adjust the attached SSCG clock.

The use of a PLL including a phase detector responsive to the phase difference between an input signal and a feedback signal and which pilots an oscillator in function of this difference, is envisaged. The PLL also includes a feedback path that is responsive to the signal generated by the oscillator and which generates said feedback signal via at least one divider with a variable division ratio. The division ratio of said divider is modulated via a sigma-delta modulator, the input of which is fed with a triangular-wave modulating signal. The preferred application is that of a spread spectrum clock generator (SSCG) for digital electronic systems.

A spread spectrum clock generator includes a phase comparator to detect a phase difference between a reference input clock signal and a feedback signal and output a control voltage, a voltage controlled oscillator to generate an output clock signal with a frequency in line with the control voltage, a phase selector to select any of equally divided phases of one cycle of the output clock signal, generate and transmit a phase shift clock signal to the phase comparator as the feedback signal, and a phase controller to decide a phase of the rising edge of the phase shift clock signal and control the phase selector to select the decided phase, and generate a second phase shift amount, decide the rising edge of the phase shift clock signal to and subject the output clock signal to spread spectrum modulation by the second phase shift amount.

A spread spectrum clock generator (SSCG) control and inspection circuit provides a system and method for inspecting and controlling an external SSCG, and for verifying the modulation profile waveform of an external SSCG. An electronic circuit is included that can check for the presence of an optimal SSCG modulation profile in product subsystems, and in attached modular systems, including electronic plug-in features such as internal network adapters and cartridges. In one mode of the invention, an electronic circuit ensures continued radiated emissions compliance for field replaceable units or consumable parts within a product, such as a printer, a scanner, or a combination (or all-in-one) printer / scanner. In another mode of the invention, an electronic circuit may also act as a secondary security device for consumable products, such as toner cartridges or ink jet cartridges. In yet another mode of the invention, an electronic circuit may also adjust the attached SSCG clock.

A spread-spectrum phase-locked loop clock generator includes a PLL circuit, a modulation generator, a bit stream processor and a multiplexer. The modulation generator outputs a bitstream in response to an input signal and a control signal. The bitstream processor generates bitstream signals. The multiplexer outputs one of the bitstream signals in response to a frequency deviation control signal. The PLL circuit is controlled by the output of the multiplexer.

This patent disclosure presents circuits, systems and methods to spread a clock signal to produce a random spreading for the clock signal that offers the maximum possible power density reduction for the spurious radiations generated from the clock signal and its harmonics. These new inventions utilize a non-linear feedback control loop to assist in generation of the spread spectrum clock and result in electronic products that can pass the FCC requirements for spurious radiations generated by the clock signal and its harmonics without utilizing expensive shielding and other EMI suppression methods.

A spread-spectrum phase-locked loop clock generator includes a PLL circuit, a modulation generator, a bit stream processor and a multiplexer. The modulation generator outputs a bitstream in response to an input signal and a control signal. The bitstream processor generates bitstream signals. The multiplexer outputs one of the bitstream signals in response to a frequency deviation control signal. The PLL circuit is controlled by the output of the multiplexer.

Spread spectrum clock generation (SSCG) using phase modulation. A first clock signal having a first frequency spectrum may be modulated using phase modulation to produce a second clock signal. The phase modulation may include providing a phase modulation profile corresponding to the integrated frequency modulation profile, to adjust a scaling factor used in obtaining the second clock signal. The phase modulation profile may be provided in the form of a pulse or pulses, which may be injected through pulse density modulation or pulse width modulation at the output of a phase frequency detector comprised in a phase locked loop circuit used in generating the second clock signal. This modified phase modulation technique removes the down spread limitation present in traditional PM implementations, and also provides better jitter performance and lower cost than traditional PM implementations.

Embodiments of the invention provide a frequency adjusting method, a system on a chip, and a terminal. According to the embodiments, when access bandwidth demands on a DDR memory change, a first frequency adjustment request for a DDR interface is generated through a CPU to adjust the operating frequency of the DDR interface; and since the operating frequency of the DDR interface is gradually adjusted according to a predetermined adjustment amount of the frequency adjustment coefficient of a spread spectrum clock generator in each adjustment and interval time between two adjacent adjustment, phase-locked loops of DLL and the spread spectrum clock generator in DDR are prevented from loss of lock, so the DDR memory can also be accessed during frequency adjustment of the DDR interface and system performance is guaranteed.

In a spread spectrum clock generator, a DLL circuit delays an oscillation clock signal from a VCO and outputs ten delay clock signals having different phases respectively. A selector selects any one of the ten delay clock signals, and outputs a selected clock signal. A control circuit controls a signal selection operation of the selector. A feedback frequency divider divides a frequency of the selected clock signal by a frequency division ratio N, and generates a comparison clock signal. In this manner, a phase of the comparison clock signal can be fine-tuned. Therefore, a spread spectrum clock generator capable of frequency modulation with high accuracy can be obtained.

A spread spectrum clock generator which includes a pulse train generator circuit and a modulating circuit configured to produce a modulating signal relating to a time derivative of an output of the pulse train generator circuit. In one embodiment the modulating circuit includes a active differentiator circuit and in another embodiment the modulating circuit includes a passive differentiator circuit. A modulator is included which is configured to produce a spread spectrum clock output which is frequency modulated by the modulating signal.

A clock signal generator varies a frequency of a digital clock over a selected range of frequencies. The generator employs a divider for lowering a frequency of a clock signal. A counter increments synchronously with the signal, and causes a selected sequence of outputs to be generated by a pattern generator. The pattern generator output forms an input to a digitally controllable delay line which receives the lower frequency clock signal. The pattern generator causes the digital delay line to vary a frequency of the lowered frequency clock signal between selected boundaries. The varying frequency clock signal is then raised up again such that a final clock has a varying frequency, and will exhibit less EMI spiking during switching of an associated, synchronous digital data device. The solid state nature of the generator allows for simple fabrication, inexpensive manufacture and ready integration into digital circuitry, such as multifunction integrated circuits.

Disclosed is a spread spectrum clock generator comprising a phase interpolator, which receives a clock signal from a clock input terminal and a control signal (an up signal and / or down signal), for adjusting the phase of an output clock signal in accordance with said control signal and outputting the resultant clock signal, and a control circuit receiving and counting the clock signal that enters from the clock input terminal and outputting said control signal (up signal or down signal), which is for varying the phase of the output clock signal based upon the result of the count, to the phase interpolator. The phase of the output clock signal from the phase interpolator varies with time and the output clock signal is frequency-modulated within a prescribed frequency range. A changeover between absence and presence of a spread spectrum clock function is performed, without a sudden fluctuation in frequency, in accordance with a frequency-modulation start signal and frequency-modulation stop signal that enters from an SSC control terminal.

A spread spectrum clock generator is provided which improves the spread spectrum effect with little increasing the circuit cost by modifying the shape of a triangular wave used for frequency modulation by as simple method. The output signal of the modulation waveform generating circuit has such a modulation waveform as indicated by solid lines in FIG. 2A. The modulation waveform is input to a VCO (voltage-controlled oscillator). In response to the modulation waveform, the oscillation frequency of the VCO is modulated, and the output clock that varies its frequency as illustrated in FIG. 2B is obtained. The frequency transition of the output clock involves such temporal variations as indicated by solid lines in FIG. 2C.

A spread spectrum clock generator includes: a phase frequency detector, for generating a phase difference signal according to a frequency divided signal and a reference signal with a reference frequency; a charge pump, for receiving the phase difference signal and generating an output current according to the phase difference signal; a loop filter, for receiving the output current and converting the output current to a voltage-controlled signal; a voltage-controlled oscillator, for receiving the voltage-controlled signal and generating a plurality of voltage-controlled output signals, wherein the plurality of voltage-controlled signals have a specific phase difference and a same voltage-controlled frequency; a frequency dividing unit, for receiving the plurality of voltage-controlled output signal and generating the frequency divided signal; and a delta-sigma modulator, for controlling the frequency dividing unit to have an equivalent divided value of (N+b)S+(N−a)(P−S) through receiving the frequency divided signal and a control word; wherein N, P, and S are integers, and a, b are fractional numbers, and S can be adjusted by the delta-sigma modulator.

An onion waveform generator and a spread spectrum clock generator (SSCG) using the same are provided. The onion waveform generator includes a value generation unit and an accumulating unit. The value generation unit outputs a counting value. The accumulating unit accumulates the counting value to output a waveform value. The accumulating unit switches from an increasing mode to a decreasing mode if the waveform value is a third boundary value, and the accumulating unit switches from the decreasing mode to the increasing mode if the waveform value is a fourth boundary value.

Spread spectrum clock generators and electronic devices including the same are provided. A spread spectrum clock generator may include an oscillation circuit that is configured to receive a first spread spectrum clock signal and to output an average frequency signal corresponding to an average frequency of the first spread spectrum clock signal. The spread spectrum clock generator may also include a phase lock loop that is configured to receive the average frequency signal and to generate a second spread spectrum clock signal. The spread spectrum clock generator may further include a control circuit that is configured to receive the first and second spread spectrum clock signals and to output a phase lock loop control signal to control the phase lock loop such that an average frequency of the second spread spectrum clock signal approaches the average frequency of the first spread spectrum clock signal.

A semiconductor device, a spread spectrum clock generator and method thereof are provided. The example semiconductor device may include a frequency dividing unit receiving an output signal, generating a first feedback signal and a second feedback signal by dividing a frequency of the received output signal, and a phase offset unit outputting the output signal having a predetermined or desired phase difference with a reference signal in response to the second feedback signal, wherein the second feedback signal having a higher frequency than the first feedback signal. The example spread spectrum clock generator may include a plurality of frequency dividers which are connected in series and a selector selecting and outputting one of a plurality of output signals, each of the plurality of output signals having a different phase difference with respect to a reference signal, in response to at least one output from one or more of the plurality of frequency dividers. The example method may include receiving a reference signal with a first frequency, generating a feedback signal having a second frequency, the second frequency higher than the first frequency and outputting at least one of a sequentially selected set of output signals in response to the generated feedback signal.

A spread spectrum clock generator includes a triangular modulator, a delta sigma modulator, a frequency divider, and a phase lock loop. The triangular modulator generates a digital modulation signal, representing a decimal, according to a digital parallel signal, in which the spread amount is in proportion to the digital parallel signal. The delta sigma modulator, electrically connected to the triangular modulator, generates a divider divisor, including the decimal and an integer, according to the digital modulation signal. The frequency divider divides the frequency of the output signal clock according to the divider divisor to generate a divided clock signal, in which the frequency of the divided clock signal is substantially equal to a quotient result from dividing the frequency of the output clock signal with the divider divisor. The phase lock loop adjusts the frequency of the output clock signal according to the divided clock signal and a reference clock signal.

A digitally controlled delay line generates a clock signal. The clock signal can be modulates as a spread spectrum clock signal. In an example embodiment, the programmable delay line has an input for receiving a signal, an output that delays outputting the input signal by a time period programmed into a delay value input. A feedback loop comprising an inverter is coupled between the input and the output of the programmable delay line.

An apparatus for transferring data in a non-spread domain to a spread domain. The apparatus comprises a first-in-first-out (FIFO) memory; a write pointer generator adapted to generate a write pointer for writing data into the FIFO memory in response to a non-spread clock signal; a spread-clock generator adapted to generate a spread clock signal based on the non-spread clock signal; a read pointer generator adapted to generate a read pointer for reading data from the FIFO memory in response to the spread clock signal; and a controller adapted to control the spread-clock generator in response to the read and write pointers indicating predetermined potential data overflow or underflow of the FIFO memory.

A spread spectrum clock generator includes a non-volatile memory to store control codes corresponding to a predetermined delay. A delay circuit receives a control code having a predetermined number of bits that determine a delay to apply to a fixed clock signal a period of time. The delay mitigates the electromagnetic interference caused by a periodic clock signal.