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Title: US7375563: Duty cycle correction using input clock and feedback clock of phase-locked-loop (PLL)
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Country: US United States of America

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Inventor: Cheung, Hung-Yan; San Jose, CA, United States of America
Zhang, Michael Y.; Palo Alto, CA, United States of America

Assignee: Pericom Semiconductor Corp., San Jose, CA, United States of America
other patents from PERICOM SEMICONDUCTOR CORP. (713978) (approx. 58)
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Published / Filed: 2008-05-20 / 2006-04-07

Application Number: US2006000308568

IPC Code: Advanced: H03L 7/06;
Core: more...

ECLA Code: H03L7/06; H03K5/156D; H03L7/18; T03L7/089C;

U.S. Class: 327/156; 327/147; 327/175; 327/176;

Field of Search: 327/154-157,159-160,162-163,165-166,170,173-176,141,144-148,150,24,208-212,218

Priority Number:
2006-04-07  US2006000308568

Abstract:     A clock generator corrects the duty cycle of an input clock. The input clock has a poor duty cycle such as less than 50%. The input clock is applied to a phase detector of a phase-locked loop (PLL). A voltage-controlled oscillator (VCO) of the PLL drives a feedback clock that is also applied to the phase detector. An edge-triggered set-reset SR flip-flop generates a duty-cycle-corrected output clock. The SR flip-flop is set by the leading edge of the input clock, but is reset by the trailing edge of the feedback clock. The VCO generates the feedback clock with the desired duty cycle, such as 50%. The leading edge of the output clock is generated by the input clock, avoiding noise generated by the PLL, while the trailing edge of the output clock is generated by the feedback clock and has PLL noise, but corrects for the desired duty cycle.

Attorney, Agent or Firm: gPatent LLC ; Auvinen, Stuart T. ;

Primary / Asst. Examiners: Lam, Tuan T.; O'Neill, Patrick

INPADOC Legal Status: Show legal status actions

Family: None

First Claim:
Show all 9 claims
    1. A duty-cycle-correcting clock generator comprising:

a phase-locked loop (PLL) that generates a feedback clock, the PLL having a phase comparator that compares phases of an input clock and the feedback clock, the PLL adjusting a frequency of the feedback clock in response to phase comparison; and

a clock toggler that receives the input clock and receives the feedback clock generated by the PLL, the clock toggler generating an output clock;

wherein the clock toggler generates leading edges of the output clock in response to leading edges of the input clock;

wherein the clock toggler generates trailing edges of the output clock in response to trailing edges of the feedback clock;

wherein the clock toggler comprises:

a flip-flop that receives the input clock at a clock input and generates the output clock;

an edge trigger circuit that receives the feedback clock and generates a reset pulse in response to a trailing edge of the feedback clock;

wherein the reset pulse is applied to a reset input of the flip-flop;

wherein the flip-flop is set by the input clock to generate a leading edge of the output clock and reset by the reset pulse to generate the trailing edge of the output clock;

wherein the PLL creates PLL noise that is included in the feedback clock but is not present in the input clock;

wherein PLL noise is propagated to trailing edges of the output clock while leading edges of the output clock do not include PLL noise,

whereby trailing edges of the output clock are generated by the PLL, and leading edges are generated by the input clock that bypasses the PLL and whereby duty cycle of the output clock is adjusted without PLL noise being added to leading edges of the output clock.



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U.S. References: Go to Result Set: All U.S. references   |  No patents reference this one   |   Backward references (16)   |   Citation Link

Buy
PDF
Patent  Pub.Date  Inventor Assignee   Title
Buy PDF- 22pp US5347232  1994-09 Nishimichi  Matsushita Electric Industrial Co. Ltd. Phase locked loop clock generator
Buy PDF- 11pp US5638016  1997-06 Eitrheim  Cyrix Corporation Adjustable duty cycle clock generator
Buy PDF- 9pp US5812619  1998-09 Runaldue  Advanced Micro Devices, Inc. Digital phase lock loop and system for digital clock recovery
Buy PDF- 52pp US5883534  1999-03 Kondoh et al.  Mitsubishi Denki Kabushiki Kaisha Waveform shaping device and clock supply apparatus
Buy PDF- 9pp US5942947  1999-08 Bhagwan  Sun Microsystems, Inc. Current-regulated, voltage-controlled oscillator with duty cycle correction
Buy PDF- 10pp US5987085  1999-11 Anderson  LSI Logic Coporation Clock recovery circuit
Buy PDF- 8pp US6295328  2001-09 Kim et al.  Hyundai Electronics Industries Co., Ltd. Frequency multiplier using delayed lock loop (DLL)
Buy PDF- 16pp US6320437  2001-11 Ma  Mosaid Technologies, Inc. Duty cycle regulator
Buy PDF- 9pp US6351508  2002-02 Shishkoff et al.  TranSwitch Corporation Phase/frequency detector for dejitter applications
Buy PDF- 10pp US6433645  2002-08 Mann et al.  Cypress Semiconductor Corp. Programmable clock generator
Buy PDF- 16pp US6452432  2002-09 Kim  Samsung Electronics Co., Ltd. Signal processing circuits having a pair of delay locked loop (DLL) circuits for adjusting a duty-cycle of a periodic digital signal and methods of operating same
Buy PDF- 24pp US6496045  2002-12 Nguyen  Xilinx, Inc. Programmable even-number clock divider circuit with duty cycle correction and optional phase shift
Buy PDF- 12pp US6583657  2003-06 Eckhardt et al.  International Business Machines Corporation Single-edge clock adjustment circuits for PLL-compatible, dynamic duty-cycle correction circuits
Buy PDF- 9pp US6822497  2004-11 Yao et al.  National Semiconductor Corporation Clock generator
Buy PDF- 11pp US20050275473A1  2005-12 Thies et al.   PLL architecture
Buy PDF- 23pp US20060012441A1  2006-01 Maneatis   Phase-locked loop with conditioned charge pump output
       
Foreign References: None

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