Clock processors in high-speed signal converter systems

• US 20090055678A1
• Filed: 08/24/2007
• Published: 02/26/2009
• Est. Priority Date: 08/24/2007
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Kummaraguntla, Ravi Kishore, Elliott, Michael
• Granted Patent: US 7,870,415 B2
• Time in Patent Office: Days
• US Class Current: 713/600
• CPC Class Codes: G06F 1/04 Generating or distributing clock signals or signals derived directly therefrom
• CPC Class Codes: G06F 1/12 Synchronisation of different clock signals provided by a plurality of clock generators
• CPC Class Codes: H03L 7/0805 the loop being adapted to provide an additional control signal for use outside the loop
• CPC Class Codes: H03L 7/0816 the controlled phase shifter and the frequency- or phase-detection arrangement being connected to a common input

Abstract

Clock processors are provided to economically control system and data clocks in high-speed signal converters. The processors generally include at least one of a delay-locked loop, phase-locked loop or a duty cycle stabilizer which generates an error signal in its operation. In the example of a stabilizer, it is configured to respond to an input clock to initiate a first portion of each cycle of the system clock and to include a control loop to provide an error signal that controls a second portion of the cycle to thereby maintain a selected duty cycle. The processors also include a data clock aligner configured to share the error signal and provide a data clock that is delayed by a selected delay from a selected one of the input and system clocks. In addition to providing effective control that is independent of disturbing effects (e.g., temperature and clock rate), the shared use reduces processor costs.

Claims

1. A clock processor for processing an input clock of a system, comprising:

a duty cycle stabilizer configured to respond to said input clock to initiate a first system portion of each system cycle of a system clock and to include a control loop to provide an error signal that controls a second system portion of said system cycle to thereby maintain a selected duty cycle of said system clock; and

a data clock aligner configured to respond to said error signal and provide a data clock that is delayed by a selected delay from said system clock.

2. The processor of claim 1, wherein said selected duty cycle is substantially 50 percent.

3. The processor of claim 1, wherein said selected delay is substantially 90 degrees.

4. The processor of claim 1, wherein said aligner is arranged to process said input clock.

5. The processor of claim 1, wherein said aligner is arranged to process said system clock.

6. The processor of claim 1, wherein said control loop is a delay-locked loop.

7. The processor of claim 6, wherein said delay-locked loop includes a delay generator formed with a current mirror and a capacitor coupled to receive a current from said current mirror.

8. The processor of claim 6, wherein said delay-locked loop includes a delay generator formed with a string of multiplexed delay elements.

9. The processor of claim 1, wherein:

said control loop includes a stabilizer delay generator configured with a stabilizer sensitivity to said error signal such that said second system portion is initiated after a selected stabilizer time delay; and

said aligner includes first and second aligner delay generators arranged to respectively initiate first and second data portions of each data cycle of said data clock and each configured to have an aligner sensitivity to said error signal such that said first and second data portions are initiated after a selected aligner time delay.

10. The processor of claim 9, wherein said control loop further includes a comparator network that provides said error signal in accordance to the difference between an average level of said system clock and a reference level.

11. The processor of claim 9, wherein:

said stabilizer further includes;

first and second stabilizer pulse generators to respectively respond to said input clock and said stabilizer delay generator; and

a stabilizer flip-flop to provide said system clock in response to said first and second stabilizer pulse generators;

and said aligner further includes;

first aligner pulse generators and second aligner pulse generators that respectively respond to a selected one of said input and system clocks and to said aligner delay generators; and

an aligner flip-flop to provide said data clock in response to said second aligner pulse generators.

12. The processor of claim 9, wherein:

said stabilizer delay generator includes;

a stabilizer capacitor;

a stabilizer current mirror that responds to said error signal; and

an inverter that couples said stabilizer current mirror to said stabilizer capacitor in response to said input clock;

and each of said first and second aligner delay generators includes;

an aligner capacitor;

an aligner current mirror that responds to said error signal; and

an inverter that couples said aligner current mirror to said aligner capacitor in response to a selected one of said input and system clocks.

13. The processor of claim 12 wherein said aligner current mirror provides a current greater than that of said stabilizer current mirror.

14. The processor of claim 9, wherein:

said stabilizer delay generator includes;

a stabilizer delay line driven by said input clock and having a stabilizer string of delay elements; and

a multiplexer to select a portion of said stabilizer string in response to said error signal,

and each of said first and second aligner delay generators includes;

an aligner delay line driven by said input clock and having an aligner string of delay elements; and

a multiplexer to select a portion of said aligner string in response to a said error signal.

16. The processor of claim 12 wherein said control loop is a delay-locked loop.

17. The processor of claim 12 wherein said control loop is a phase-locked loop.

20. The system of claim 17, wherein said control loop is a delay-locked loop that includes a delay generator formed with a string of delay elements.

15. A clock processor for processing an input clock of a system, comprising:

a control loop that includes a delay network and is configured to apply an error signal to said delay network for generation of an output clock in response to said input clock; and

a data clock aligner that includes first and second aligner delay generators arranged to respectively initiate first and second data portions of each data cycle of a data clock that is delayed by a selected delay from said system clock wherein said first and second aligner delay generators are each configured to have an aligner sensitivity to said error signal such that said first and second data portions are initiated after a selected aligner time delay.

18. A signal converter system for converting an analog input signal into a corresponding digital code in response to an input clock, the system comprising:

a pipelined arrangement of converter stages that successively process said input signals to corresponding digital bits in response to a system clock derived from said input clock;

an alignment/correction logic configured to process said digital bits into said digital code;

a duty cycle stabilizer configured to respond to said input clock to initiate a first system portion of each system cycle of said system clock and to include a control loop to provide an error signal that controls a second system portion of said system cycle to thereby maintain a selected duty cycle of said system clock; and

a data clock aligner configured to respond to said error signal and provide a data clock that is delayed by a selected delay from said system clock wherein said data clock provides a temporal reference for said digital code.

19. The system of claim 18, wherein said control loop is a delay-locked loop that includes a delay generator formed with a current mirror and a capacitor arranged to receive a current from said current mirror.