Duty Cycle Phase Interpolation for Low-Nonlinearity Clock Alignment

Solution Overview

Problem

Existing clock signal interpolation methods, such as mixer-based analog interpolators, face challenges in achieving precise phase alignment due to high power and area costs, as well as significant integral non-linearity, which complicates and consumes extra resources for signal pre- and post-processing.

Innovation Solution

A duty cycle-based phase interpolator circuit using pulse width modulators and state machines to produce variable duty cycle signals, allowing for arbitrary phase shifts by adjusting current inputs, thereby aligning clock signals with data eye centers and synchronizing multiple system components without the need for costly pre- and post-processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If mixer-based analog interpolators are used to adjust clock phase, then phase alignment capability is achieved, but power consumption and circuit area increase significantly

Engineering Contradiction:

Improvephase alignment precisionVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the analog mixer-based mechanical/electrical system with a digital logic-based system. Specifically, it uses digital pulse width modulators, state machines, and logic circuits to achieve phase interpolation, eliminating the need for analog mixers and current mirrors. This substitution fundamentally changes the approach from analog signal processing to digital logic operations, resolving the power consumption issue while maintaining phase alignment capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters by using duty cycle modulation instead of analog amplitude mixing. The digital phase interpolator varies the duty cycle of clock signals (50% to 100%) and uses state machines to interpret these duty cycle variations as phase information. This parameter change from analog amplitude to digital duty cycle enables precise phase control with significantly reduced power consumption

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If mixer-based analog interpolators are used to adjust clock phase, then phase alignment capability is achieved, but circuit area increases significantly

Engineering Contradiction:

Improvephase alignment precisionVSAvoidcircuit area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent replaces the analog mixer-based mechanical/electrical system with a digital logic-based system. Specifically, it uses digital pulse width modulators, state machines, and logic circuits to achieve phase interpolation, eliminating the need for analog mixers and current mirrors. This substitution fundamentally changes the approach from analog signal processing to digital logic operations, resolving the power consumption issue while maintaining phase alignment capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The digital phase interpolator uses universal digital logic components (state machines, pulse width modulators, logic gates) that can perform multiple functions. The same digital circuitry that generates and processes duty cycle signals also performs phase detection, interpolation, and output generation, eliminating the need for separate analog mixer circuits and reducing overall circuit area

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If mixer-based analog interpolators are used, then phase adjustment is possible, but integral non-linearity increases requiring costly pre- and post-processing

Engineering Contradiction:

Improvephase adjustment capabilityVSAvoidintegral non-linearity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent replaces the analog mixer-based mechanical/electrical system with a digital logic-based system. Specifically, it uses digital pulse width modulators, state machines, and logic circuits to achieve phase interpolation, eliminating the need for analog mixers and current mirrors. This substitution fundamentally changes the approach from analog signal processing to digital logic operations, resolving the power consumption issue while maintaining phase alignment capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The digital phase interpolator inherently produces linear phase relationships through its digital logic operation. The state machine and pulse width modulator automatically generate correctly proportioned phase outputs without requiring external pre-processing or post-processing circuits. The system self-corrects for linearity issues that plague analog mixers, eliminating the need for costly additional processing stages

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS8581651B2Duty cycle based phase interpolators and methods for use

Publication Date: 2013.11.12 MICRON TECHNOLOGY INC

AI summary

Duty cycle based phase interpolators, and methods for implementing duty cycle based phase interpolators are disclosed. One such phase interpolator includes a first pulse width modulator configured to generate a first duty cycle signal, and a second pulse width modulator configured to generate a second duty cycle signal. The phase interpolator further includes a logic unit configured to merge the first duty cycle signal and the second duty cycle signal to produce a periodic digital signal with a controllable phase depending on the first and second duty cycle signals.