Patents by Inventor Nestor Tzartzanis

Nestor Tzartzanis has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 8718217
    Abstract: In one embodiment, a circuit includes a voltage-controlled oscillator (VCO) configured to generate k first clock signals that each have a first phase based on a charge-pump control voltage signal; one or more phase interpolators (PIs) configured to receive the k first clock signals and one or more first feedback controls signals and generate m second clock signals that each have a second phase based on the k first clock signals and the one or more first feedback control signals; a first phase detector (PD) configured to receive the m second clock signals and generate the one or more first feedback control signals based on the m second clock signals; a second PD configured to generate one or more second feedback control signals based on the m second clock signals; and a charge pump configured to output the charge-pump control voltage signal based on the second feedback control signals.
    Type: Grant
    Filed: July 29, 2009
    Date of Patent: May 6, 2014
    Assignee: Fujitsu Limited
    Inventors: William W. Walker, H. Anders Kristensson, Nikola Nedovic, Nestor Tzartzanis
  • Patent number: 8411782
    Abstract: In one embodiment, a method includes receiving input data bits at a collective data rate, the input data bits being grouped into a plurality of input data words, the input data bits of each of the input data words being received from n parallel input-data-bit streams, each of the n parallel input-data-bit streams having a stream data rate that is 1/n of the collective data rate, each of the input data words comprising n consecutive ones of the input data bits; selecting particular input data bits; and generating a k-bit deskew channel with the selected input data bits, the deskew channel comprising a number of frames, each of the frames comprising x input data bits from one or more input data words and one or more framing bits. In another embodiment, a method includes using such a deskew channel to determine relative delays between data channels and the deskew channel.
    Type: Grant
    Filed: July 29, 2009
    Date of Patent: April 2, 2013
    Assignee: Fujitsu Limited
    Inventors: Samir Parikh, William W. Walker, Nestor Tzartzanis
  • Patent number: 8300754
    Abstract: In one embodiment, a method includes receiving first and second input streams comprising first and second input data bits, respectively. The method includes generating first and second recovered clocks based on the first and second input streams, respectively. The method includes retiming and demultiplexing the first and second input data bits to generate n first recovered streams and n second recovered streams, respectively, each comprising first and second recovered data bits, respectively. The method further includes determining a phase difference between the first and second recovered clocks; aligning the first recovered data bits with the second recovered data bits based at least in part on a value of n and the phase difference; combining the first and second recovered data bits to generate an output stream; and retiming the first and second recovered data bits in the output stream based on either the first or second recovered clock.
    Type: Grant
    Filed: July 27, 2009
    Date of Patent: October 30, 2012
    Assignee: Fujitsu Limited
    Inventors: Nikola Nedovic, Nestor Tzartzanis, William W. Walker, Hirotaka Tamura
  • Patent number: 8300753
    Abstract: In one embodiment, a method includes accessing a reference clock having a reference clock frequency and reference clock phase; generating an output clock having an output clock phase and output clock frequency that is a function of an analog control voltage setting and a frequency gain curve; fixing the analog control voltage setting to a predetermined voltage; selecting one of the frequency gain curves within a predetermined frequency range of the reference clock frequency at the analog control voltage setting; adjusting the analog control voltage setting to adjust the output clock frequency to be within another predetermined frequency range of the reference clock frequency; and adjusting the output clock phase to be within a predetermined phase range of an input data phase of the input data stream.
    Type: Grant
    Filed: July 27, 2009
    Date of Patent: October 30, 2012
    Assignee: Fujitsu Limited
    Inventors: Nikola Nedovic, Nestor Tzartzanis, William W. Walker
  • Patent number: 8058914
    Abstract: In one embodiment, a circuit includes a first circuit input for receiving a first reference signal having a first phase; a second circuit input for receiving a second reference signal having a second phase; a third circuit input for receiving a target phase signal; a circuit output for outputting an output signal; a first multiplying mixer cell (MMC) comprising a first MMC input, a second MMC input, and a first MMC output; a second MMC comprising a third MMC input, a fourth MMC input, and a second MMC output.
    Type: Grant
    Filed: July 29, 2009
    Date of Patent: November 15, 2011
    Assignee: Fujitsu Limited
    Inventors: H. Anders Kristensson, Nestor Tzartzanis, Nikola Nedovic, William W. Walker
  • Publication number: 20100104057
    Abstract: In one embodiment, a method includes receiving first and second input streams comprising first and second input data bits, respectively. The method includes generating first and second recovered clocks based on the first and second input streams, respectively. The method includes retiming and demultiplexing the first and second input data bits to generate n first recovered streams and n second recovered streams, respectively, each comprising first and second recovered data bits, respectively. The method further includes determining a phase difference between the first and second recovered clocks; aligning the first recovered data bits with the second recovered data bits based at least in part on a value of n and the phase difference; combining the first and second recovered data bits to generate an output stream; and retiming the first and second recovered data bits in the output stream based on either the first or second recovered clock.
    Type: Application
    Filed: July 27, 2009
    Publication date: April 29, 2010
    Applicant: Fujitsu Limited
    Inventors: Nikola Nedovic, Nestor Tzartzanis, William W. Walker, Hirotaka Tamura
  • Publication number: 20100091927
    Abstract: In one embodiment, a circuit includes a voltage-controlled oscillator (VCO) configured to generate k first clock signals that each have a first phase based on a charge-pump control voltage signal; one or more phase interpolators (PIs) configured to receive the k first clock signals and one or more first feedback controls signals and generate m second clock signals that each have a second phase based on the k first clock signals and the one or more first feedback control signals; a first phase detector (PD) configured to receive the m second clock signals and generate the one or more first feedback control signals based on the m second clock signals; a second PD configured to generate one or more second feedback control signals based on the m second clock signals; and a charge pump configured to output the charge-pump control voltage signal based on the second feedback control signals.
    Type: Application
    Filed: July 29, 2009
    Publication date: April 15, 2010
    Applicant: Fujitsu Limited
    Inventors: William W. Walker, H. Anders Kristensson, Nikola Nedovic, Nestor Tzartzanis
  • Publication number: 20100090733
    Abstract: In one embodiment, a circuit includes a first circuit input for receiving a first reference signal having a first phase; a second circuit input for receiving a second reference signal having a second phase; a third circuit input for receiving a target phase signal; a circuit output for outputting an output signal; a first multiplying mixer cell (MMC) comprising a first MMC input, a second MMC input, and a first MMC output; a second MMC comprising a third MMC input, a fourth MMC input, and a second MMC output.
    Type: Application
    Filed: July 29, 2009
    Publication date: April 15, 2010
    Applicant: Fujitsu Limited
    Inventors: H. Anders Kristensson, Nestor Tzartzanis, Nikola Nedovic, William W. Walker
  • Publication number: 20100091925
    Abstract: In one embodiment, a method includes accessing a reference clock having a reference clock frequency and reference clock phase; generating an output clock having an output clock phase and output clock frequency that is a function of an analog control voltage setting and a frequency gain curve; fixing the analog control voltage setting to a predetermined voltage; selecting one of the frequency gain curves within a predetermined frequency range of the reference clock frequency at the analog control voltage setting; adjusting the analog control voltage setting to adjust the output clock frequency to be within another predetermined frequency range of the reference clock frequency; and adjusting the output clock phase to be within a predetermined phase range of an input data phase of the input data stream.
    Type: Application
    Filed: July 27, 2009
    Publication date: April 15, 2010
    Applicant: Fujitsu Limited
    Inventors: Nikola Nedovic, Nestor Tzartzanis, William W. Walker
  • Publication number: 20100086075
    Abstract: In one embodiment, a method includes receiving input data bits at a collective data rate, the input data bits being grouped into a plurality of input data words, the input data bits of each of the input data words being received from n parallel input-data-bit streams, each of the n parallel input-data-bit streams having a stream data rate that is 1/n of the collective data rate, each of the input data words comprising n consecutive ones of the input data bits; selecting particular input data bits; and generating a k-bit deskew channel with the selected input data bits, the deskew channel comprising a number of frames, each of the frames comprising x input data bits from one or more input data words and one or more framing bits. In another embodiment, a method includes using such a deskew channel to determine relative delays between data channels and the deskew channel.
    Type: Application
    Filed: July 29, 2009
    Publication date: April 8, 2010
    Applicant: Fujitsu Limited
    Inventors: Samir Parikh, William W. Walker, Nestor Tzartzanis
  • Publication number: 20100085086
    Abstract: In one embodiment, a method is described that includes receiving a first clock signal and a second clock signal; dividing the first clock signal by a value of n to generate a divided first clock signal; sampling the frequency detector the divided first clock signal with the second clock signal to generate a plurality of samples; generating a first adjustment signal if more than a predetermined number of consecutive samples in a set of consecutive samples have identical logical values; and generating a second adjustment signal if less than the predetermined number of consecutive samples in the set of consecutive samples have identical logical values.
    Type: Application
    Filed: July 27, 2009
    Publication date: April 8, 2010
    Applicant: Fujitsu Limited
    Inventors: Nikola Nedovic, Nestor Tzartzanis, William W. Walker
  • Patent number: 7626425
    Abstract: High performance clock-powered logic runs at below supply levels and reduces the need for faster digital logic circuitry. In a preferred embodiment, a clocked buffer is used to drive the signal line. The receiving end of the line is connected to a jam latch, preferably followed by an n-latch, followed by the digital logic, and followed by a second n-latch. The first n-latch is eliminated in an alternate embodiment, preferably one that uses complementary data signals.
    Type: Grant
    Filed: January 13, 2006
    Date of Patent: December 1, 2009
    Assignee: University of Southern California
    Inventors: William C. Athas, Nestor Tzartzanis, Weihua Mao, Lena Peterson
  • Patent number: 7616070
    Abstract: Disclosed are multiphase oscillators comprising a plurality of delay stages serially coupled in a loop by a plurality of nodes, with the loop being folded to provide two concentric rings of delay stages with equal numbers of allocated nodes. A second plurality of negative-resistance elements are provided, each element having a first output coupled to a node on the first concentric ring and a second output coupled to a node on the second concentric ring. Each such output switches between first and second voltage levels, and provides a negative resistance to a signal coupled to it during at least a portion of the transition between voltage levels. The outputs of an element switch to opposite voltage levels. With this construction, a high-voltage pulse propagates around the loop of delay stages, with a low-voltage pulse propagating behind it. Also disclosed are circuits to control the direction of pulse propagation.
    Type: Grant
    Filed: November 5, 2007
    Date of Patent: November 10, 2009
    Assignee: Fujitsu Limited
    Inventors: Nestor Tzartzanis, William W. Walker
  • Patent number: 7405593
    Abstract: Disclosed are on-chip global electrical signaling systems and methods employing differential current-mode sensing having reduced delay and energy dissipation compared to conventional inverter repeaters. The present inventions can be used for point-to-point connections as well as N-to-1 connections.
    Type: Grant
    Filed: November 1, 2005
    Date of Patent: July 29, 2008
    Assignee: Fujitsu Limited
    Inventors: Nestor Tzartzanis, William W. Walker
  • Publication number: 20080061896
    Abstract: Disclosed are multiphase oscillators comprising a plurality of delay stages serially coupled in a loop by a plurality of nodes, with the loop being folded to provide two concentric rings of delay stages with equal numbers of allocated nodes. A second plurality of negative-resistance elements are provided, each element having a first output coupled to a node on the first concentric ring and a second output coupled to a node on the second concentric ring. Each such output switches between first and second voltage levels, and provides a negative resistance to a signal coupled to it during at least a portion of the transition between voltage levels. The outputs of an element switch to opposite voltage levels. With this construction, a high-voltage pulse propagates around the loop of delay stages, with a low-voltage pulse propagating behind it. Also disclosed are circuits to control the direction of pulse propagation.
    Type: Application
    Filed: November 5, 2007
    Publication date: March 13, 2008
    Applicant: Fujitsu Limited
    Inventors: Nestor Tzartzanis, William Walker
  • Patent number: 7307483
    Abstract: Disclosed are multiphase oscillators comprising a plurality of delay stages serially coupled in a loop by a plurality of nodes, with the loop being folded to provide two concentric rings of delay stages with equal numbers of allocated nodes. A second plurality of negative-resistance elements are provided, each element having a first output coupled to a node on the first concentric ring and a second output coupled to a node on the second concentric ring. Each such output switches between first and second voltage levels, and provides a negative resistance to a signal coupled to it during at least a portion of the transition between voltage levels. The outputs of an element switch to opposite voltage levels. With this construction, a high-voltage pulse propagates around the loop of delay stages, with a low-voltage pulse propagating behind it. Also disclosed are circuits to control the direction of pulse propagation.
    Type: Grant
    Filed: February 3, 2006
    Date of Patent: December 11, 2007
    Assignee: Fujitsu Limited
    Inventors: Nestor Tzartzanis, William W. Walker
  • Publication number: 20070182497
    Abstract: Disclosed are multiphase oscillators comprising a plurality of delay stages serially coupled in a loop by a plurality of nodes, with the loop being folded to provide two concentric rings of delay stages with equal numbers of allocated nodes. A second plurality of negative-resistance elements are provided, each element having a first output coupled to a node on the first concentric ring and a second output coupled to a node on the second concentric ring. Each such output switches between first and second voltage levels, and provides a negative resistance to a signal coupled to it during at least a portion of the transition between voltage levels. The outputs of an element switch to opposite voltage levels. With this construction, a high-voltage pulse propagates around the loop of delay stages, with a low-voltage pulse propagating behind it. Also disclosed are circuits to control the direction of pulse propagation.
    Type: Application
    Filed: February 3, 2006
    Publication date: August 9, 2007
    Inventors: Nestor Tzartzanis, William Walker
  • Publication number: 20070103199
    Abstract: Disclosed are on-chip global electrical signaling systems and methods employing differential current-mode sensing having reduced delay and energy dissipation compared to conventional inverter repeaters. The present inventions can be used for point-to-point connections as well as N-to-1 connections.
    Type: Application
    Filed: November 1, 2005
    Publication date: May 10, 2007
    Inventors: Nestor Tzartzanis, William Walker
  • Publication number: 20070018689
    Abstract: High performance clock-powered logic runs at below supply levels and reduces the need for faster digital logic circuitry. In a preferred embodiment, a clocked buffer is used to drive the signal line. The receiving end of the line is connected to a jam latch, preferably followed by an n-latch, followed by the digital logic, and followed by a second n-latch. The first n-latch is eliminated in an alternate embodiment, preferably one that uses complementary data signals.
    Type: Application
    Filed: January 13, 2006
    Publication date: January 25, 2007
    Applicant: University of Southern California
    Inventors: William Athas, Nestor Tzartzanis, Weihua Mao, Lena Peterson
  • Patent number: 7075842
    Abstract: Disclosed is a memory architecture where current sense amplifiers are used instead of voltage sense amplifiers, and where the memory cells normally disposed along a single bit line are divided between two half bit lines. Each half bit line is coupled to a respective input of the current sense amplifier. When one of the memory cells is selected for reading, it couples a current related to its stored data state to the half bit line that it is coupled to. During this operation, a reference current is generated on the other half bit line. Also disclosed are novel current sense amplifiers.
    Type: Grant
    Filed: February 13, 2004
    Date of Patent: July 11, 2006
    Assignee: Fujitsu Limited
    Inventors: Nestor Tzartzanis, William W. Walker