Multi-Stage Phase Interpolator for Clock Edge Alignment

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Solution Overview

Problem

Existing integrated circuits face challenges in precisely aligning signal edges due to manufacturing errors and power-supply noise, leading to phase vector distortion and integral non-linearity.

Innovation Solution

A multi-stage phase interpolator is used to select phase vectors closest to the desired edge alignment, interpolate between them, and apply tailored interpolation functions to correct for distortion, thereby improving edge timing and phase alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a phase interpolator is used to align clock signals, then phase alignment is improved, but manufacturing errors and power-supply noise cause phase vector distortion and integral non-linearity

Engineering Contradiction:

Improvephase alignment precisionVSAvoidphase vector distortion

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The phase interpolator is divided into multiple stages: a first stage that selects phase vectors and a second stage that interpolates between selected phase vectors. This segmentation allows each stage to address specific aspects of phase alignment, improving overall precision while managing the complexity introduced by manufacturing errors and noise

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies tailored interpolation functions in the second stage that are specific to each selected pair of phase vectors. This local quality approach corrects for distortion that varies between different phase vectors, addressing the reliability issue caused by manufacturing errors and power-supply noise while maintaining high phase alignment precision

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If multiple phase vectors are used to cover a unit interval, then phase coverage is improved, but distortion varies between phase vectors causing integral non-linearity

Engineering Contradiction:

Improvephase coverageVSAvoidintegral non-linearity

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent dynamically selects different interpolation functions based on which pair of phase vectors is being used. This dynamic adaptation allows the system to maintain high phase coverage across the unit interval while compensating for the varying distortion characteristics of different phase vector pairs, thereby reducing integral non-linearity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The interpolation function parameters are changed depending on the selected phase vector pair. By adjusting these parameters to account for distortion variations, the system maintains accurate phase alignment across all phase vectors while compensating for manufacturing-induced non-linearity

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12316327B2Phase interpolator with sub-period phase correction

Publication Date: 2025.05.27 RAMBUS INC

AI summary

A phase interpolator circuit has a first stage that selects a pair of phase vectors from among M available sets of pairs and a second stage that interpolates between the selected pair to phase align a sample clock. The interpolation functions applied to selected pairs of phase vectors can differ to account for integral non-linearity, duty-cycle distortion, phase errors, and crosstalk that vary between phase vectors.