Voltage-Follower Cross-Coupled Oscillators for Phase Tuning

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Solution Overview

Problem

Conventional phase interpolator circuits in high-speed clocking systems are expensive in terms of power consumption and circuit area, and inverter-based cross-coupling in differential oscillators leads to a 30-40% reduction in oscillation frequency, making them inefficient for high-frequency applications.

Innovation Solution

The use of tunable cross-coupling elements in an assistant loop circuit to lock phase relationships among multiple oscillators, allowing for fine phase tunability without the need for self-oscillation or full voltage swing, thereby integrating the phase interpolator circuit into the oscillator with reduced power and area requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If inverter-based cross-coupling is used in differential oscillators, then signal phase correlation is improved, but oscillation frequency is reduced by 30-40%

Engineering Contradiction:

Improvesignal phase correlationVSAvoidoscillation frequency

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The patent introduces voltage follower circuits as intermediary elements between the ring oscillator stages and the cross-coupling network. These voltage followers act as buffer mediators that isolate the oscillation core from the phase-correlating cross-coupling elements, preventing the latter from loading and slowing down the former while still achieving the desired phase correlation effect.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the oscillator into distinct functional blocks: the ring oscillator core that generates the fundamental frequency, and the cross-coupling network that provides phase correlation. By separating the frequency-generating function from the phase-correlating function, the design allows each block to operate optimally without compromising the other's performance.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If conventional phase interpolator circuits are used, then phase tuning capability is improved, but power consumption and circuit area increase

Engineering Contradiction:

Improvephase tuning capabilityVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent merges the phase interpolator functionality directly into the oscillator structure by using the same voltage follower circuits that provide cross-coupling to also perform phase interpolation. This integration eliminates the need for separate, dedicated phase interpolator circuits, thereby reducing both power consumption and circuit area while maintaining full phase tuning capability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The voltage follower circuits are designed to serve multiple functions simultaneously: they provide cross-coupling for phase correlation, enable phase interpolation for tuning, and act as buffers for impedance matching. This multi-functionality reduces the overall circuit complexity and resource requirements compared to conventional designs that use separate circuits for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If conventional phase interpolator circuits are used, then phase tuning capability is improved, but circuit area increases

Engineering Contradiction:

Improvephase tuning capabilityVSAvoidcircuit area

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

4Speed

If high frequency oscillation is targeted, then data rate capability is improved, but oscillator design complexity increases

Engineering Contradiction:

Improvedata rate capabilityVSAvoidoscillator design complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The voltage follower circuits serve as intermediary buffer stages that isolate the high-speed oscillation core from the load effects of the cross-coupling and phase interpolation networks. This buffering allows the ring oscillator to maintain its high frequency operation without being degraded by the complexity of the additional functional blocks.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the oscillator into distinct functional blocks with clear interfaces, allowing each block to be optimized independently for high-frequency operation. The modular structure makes the overall complex system more manageable and easier to design at high frequencies compared to monolithic approaches.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10742224B2Voltage-follower based cross-coupling oscillators with embedded phase-interpolation function

Publication Date: 2020.08.11 NVIDIA CORP

AI summary

A circuit includes a first ring oscillator with a plurality of stages, each coupled via a voltage follower cross-coupling to a plurality of stages of a second ring oscillator. Further ring oscillators may be coupled to the first ring oscillator and the second ring oscillator. Additionally, the voltage follower cross-coupling for each of the stages may include one or more first voltage follower having a first strength, and one or more second voltage follower having a second strength different than the first strength.