INTEGRATED CIRCUIT COMPRISING CIRCUITRY TO DETERMINE SETTINGS FOR AN INJECTION-LOCKED OSCILLATOR

• US 20150333760A1
• Filed: 01/03/2014
• Published: 11/19/2015
• Est. Priority Date: 01/08/2013
• Status: Active Grant

• Current Assignee: Rambus Inc.
• Original Assignee: Rambus Inc.
• Inventors: Zerbe, Jared L., Hossain, Masum
• Granted Patent: US 9,735,792 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H03K 3/0307 Stabilisation of output, e.g. using crystal
• CPC Class Codes: H03K 3/0315 Ring oscillators
• CPC Class Codes: H03L 1/00 Stabilisation of generator output against variations of physical values, e.g. power supply
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or phase-locked loop
• CPC Class Codes: H03L 7/083 the reference signal being additionally directly applied to the generator
• CPC Class Codes: H03L 7/089 the phase or frequency detector generating up-down pulses H03L7/087 takes precedence
• CPC Class Codes: H03L 7/24 using a reference signal directly applied to the generator

Abstract

Embodiments of an integrated circuit (IC) comprising circuitry to determine settings for an injection-locked oscillator (ILO) are described. In some embodiments, an injection signal is generated based on a first clock edge of a reference clock signal, and is injected into an ILO. Next, one or more output signals of the ILO are sampled based on a second clock edge of the reference clock signal, and settings for the ILO are determined based on the samples. In some embodiments, a sequence of two or more time-to-digital (TDC) codes is generated based on a reference clock signal and a free-running ILO. In some embodiments, the TDC circuitry that is already present in a delay-locked loop is reused for determining the sequence of two or more TDC codes. The ILO settings can then be determined based on the sequence of two or more TDC codes.

Claims

1. An integrated circuit (IC), comprising:

an injection-locked oscillator (ILO) to generate a set of oscillating signals having different phases, wherein the ILO has a natural oscillation frequency;

first circuitry to inject at least one injection signal into at least one injection location of the ILO, wherein the injection signal is generated based on a first clock edge of a reference clock signal having a reference clock frequency;

second circuitry to obtain one or more samples by sampling the set of oscillating signals based on a second clock edge of the reference clock signal; and

third circuitry to determine settings for the ILO based on the one or more samples, wherein the settings correspond to the natural oscillation frequency being substantially equal to the reference clock frequency or an integral multiple of the reference clock frequency.

2. The IC of claim 1, wherein the first circuitry is capable of injecting multiple delayed versions of the pulse at multiple injection locations of the ILO.

3. The IC of claim 1, wherein after injecting the injection signal corresponding to the first clock edge of the reference clock signal, the first circuitry is capable of preventing subsequent injection signals corresponding to subsequent clock edges of the reference clock signal from being injected into the ILO.

4. The IC of claim 1, wherein the ILO includes a set of delay stages, and wherein the set of oscillating signals correspond to output signals of at least a subset of the set of delay stages.

5. The IC of claim 4, wherein the second circuitry includes at least two edge-triggered flip-flops, wherein outputs of at least two different delay stages are coupled to inputs of the at least two edge-triggered flip-flops.

6. The IC of claim 5, wherein the third circuitry includes logic to determine a delay-element setting by performing a table lookup based on values stored in the at least two edge-triggered flip-flops.

7. An integrated circuit (IC), comprising:

an injection-locked oscillator (ILO) to generate a set of oscillating signals having different phases, wherein the ILO has a natural oscillation frequency;

first circuitry to obtain a set of samples by sampling the set of oscillating signals based on a reference clock signal having a reference clock frequency;

second circuitry to determine a sequence of two or more codes, wherein each code in the sequence of two or more codes is determined based on a set of samples that was obtained when the set of oscillating signals was sampled at a clock edge of the reference clock signal, and wherein different codes in the sequence of two or more codes correspond to different clock edges of the reference clock signal that were used for sampling the set of oscillating signals;

third circuitry to determine settings for the ILO based on the sequence of two or more codes, wherein the settings correspond to the natural oscillation frequency being substantially equal to the reference clock frequency or an integral multiple of the reference clock frequency.

8. The IC of claim 7, further comprising fourth circuitry to prevent an injection signal from being injected into the ILO.

9. The IC of claim 7, wherein the third circuitry includes fourth circuitry to determine a delay-element setting by performing a table lookup based on a value that is computed using the sequence of two or more codes.

10. The IC of claim 9, further comprising fifth circuitry to provide the delay-element setting to the ILO.

11. A method, comprising:

injecting at least one injection signal into at least one injection location of an injection locked oscillator (ILO) having a natural oscillation frequency, wherein the injection signal is generated based on a first clock edge of a reference clock signal having a reference clock frequency, and wherein the ILO generates a set of oscillating signals having different phases;

obtaining one or more samples by sampling the set of oscillating signals based on a second clock edge of the reference clock signal; and

determining settings for the ILO based on the one or more samples, wherein the settings correspond to the natural oscillation frequency being substantially equal to the reference clock frequency or an integral multiple of the reference clock frequency.

12. The method of claim 11, wherein after injecting the injection signal corresponding to the first clock edge of the reference clock signal, the method further comprises preventing subsequent injection signals corresponding to subsequent clock edges of the reference clock signal from being injected into the ILO.

13. The method of claim 11, wherein said determining includes determining a delay-element setting by performing a table lookup based on the one or more samples.

14. The method of claim 11, wherein the method is performed when one or more of the following events occur:

a clock drift in the reference clock signal is greater than a threshold,

a change in a temperature value is greater than a threshold, and

a change in a supply voltage value is greater than a threshold.

15-19. -19. (canceled)