Circuit Path Signal Inversion for Timing Skew Cancellation

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Solution Overview

Problem

Timing skew in circuit paths, resulting from differences in rising and falling edge delays, leads to signal distortion and reduced design margins, making it challenging to maintain minimum pulse width and detectability in automatic test equipment and integrated circuits.

Innovation Solution

The method involves controlling signal states in a circuit path by inverting or not inverting signals using multiplexers and inverter circuitry, allowing different circuits to skew signals in opposite directions, thereby canceling out skews and reducing overall skew in the circuit path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If circuits are electrically connected in series in the circuit path, then signal transmission is achieved, but timing skew increases causing signal distortion

Engineering Contradiction:

Improvesignal integrityVSAvoidtiming skew

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies inversion by switching the polarity state of circuits in the series connection. By inverting the state of alternate circuits (e.g., changing from non-inverting to inverting mode), the skew introduced by each circuit is reversed, causing skews to cancel each other out. This allows the series connection to maintain signal transmission while reducing cumulative timing skew.

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If signal polarity is inverted to reduce skew, then timing skew is reduced, but circuit complexity increases

Engineering Contradiction:

Improvetiming skew controlVSAvoidcircuit configuration

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent implements dynamics by making the circuit polarity state switchable rather than fixed. Control circuitry dynamically adjusts the state of circuits (inverting or non-inverting mode) based on measured skew characteristics. This dynamic reconfiguration allows the system to adapt to different skew conditions without requiring multiple fixed circuit designs, thereby managing complexity through programmable control.

Inventive Principle:

Principle #15Dynamics

3Reliability

If skew cancellation is achieved through state control, then signal detectability is improved, but measurement and control difficulty increases

Engineering Contradiction:

Improvesignal detectabilityVSAvoidskew measurement

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent employs feedback by measuring the actual skew in the circuit path and using this measurement to control the polarity state of circuits. The control circuitry receives skew information (either from direct measurement or pre-characterized data) and adjusts circuit states accordingly to achieve skew cancellation. This closed-loop feedback mechanism simplifies the control process by automatically adapting to measured conditions rather than requiring manual calibration.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12041713B2Reducing timing skew in a circuit path

Publication Date: 2024.07.16 TERADYNE INC

AI summary

An example method performed for a circuit path includes: receiving signals in the circuit path; and controlling states of the signals in the circuit path based on skews produced by circuits electrically connected in series in the circuit path. The states are controlled by inverting or not inverting the signals in the circuit path so that skews produced by different circuits in the circuit paths at least partially cancel.