Shield Structure for Single-Ended Clock Crosstalk Isolation
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Solution Overview
Problem
High-frequency clock distribution circuits face challenges with crosstalk-induced jitter, which limits the clock distribution span and requires increased power consumption and chip area when using differential clock signals.
Innovation Solution
A shield structure, comprising a shield wall and/or shield cage, is used to mitigate crosstalk between single-ended clock lines, allowing for increased clock distribution span within specified jitter limits, reducing power and area requirements by using single-ended clock lines instead of differential ones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If differential clock signals are used to mitigate crosstalk, then crosstalk and jitter are reduced, but power consumption increases and chip area occupied increases
Solution Approach 1:
A shield structure (shield wall or shield cage) is introduced as an intermediary element between clock lines to block electromagnetic fields and reduce crosstalk. The shield acts as a mediator that prevents direct coupling between adjacent clock lines, achieving crosstalk mitigation similar to differential signaling but with single-ended lines that consume less power.
Solution Approach 2:
The patent changes the physical parameters of the clock distribution system by introducing shielding structures with specific geometries (shield wall height, shield cage dimensions, opening patterns). These parameter changes modify the electromagnetic environment to reduce crosstalk while maintaining single-ended operation, avoiding the need for differential signaling's higher power consumption.
2Reliability
If differential clock signals are used to mitigate crosstalk, then crosstalk and jitter are reduced, but chip area occupied increases
Solution Approach 1:
The shield structure serves as a space-efficient intermediary that provides crosstalk protection without requiring the paired line configuration of differential signaling. By placing shields between or around single-ended lines, the patent achieves reliable crosstalk mitigation while occupying less chip area than differential clock distributions would require.
3Use of energy by moving object
If single-ended clock lines are used without shielding, then power consumption and chip area are reduced, but crosstalk and jitter increase
Solution Approach 1:
The patent optimizes the parameters of the shield structure (height, width, positioning, opening patterns) to achieve effective crosstalk reduction with minimal impact on power consumption and area. By carefully tuning these parameters, the shield provides just enough protection to meet jitter requirements while maintaining the power and area advantages of single-ended signaling.
4Length of stationary object
If clock lines run alongside each other for long distance, then clock distribution span is extended, but crosstalk and jitter increase
Solution Approach 1:
The shield structure is positioned alongside clock lines for portions of their length, providing continuous crosstalk protection over extended distribution spans. The shield acts as a moving boundary that follows the clock lines, enabling long-distance distribution while maintaining signal integrity by blocking cumulative crosstalk effects that would otherwise build up over distance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The shield structure effectively reduces crosstalk and associated jitter, enabling longer clock distribution distances while minimizing power consumption and chip area, achieving isolation comparable to differential clock signals.
Implementation Method 1
a shield structure, comprising a shield wall and/or shield cage, is used to mitigate crosstalk between single-ended clock lines
Data Source
AI summary
An integrated circuit is described. The integrated circuit includes a first layer, a first clock line for carrying a first clock signal, and a second clock line for carrying a second clock signal. The second clock line runs alongside the first clock line for a distance. The integrated circuit includes a shield structure for shielding the clock line from crosstalk and/or other interference. The shield structure includes a shield wall extending from the first layer. The shield wall runs between the first and second clock lines for at least a portion of the distance. The shield structure may also include a shield cage extending from the first layer and surrounding the first and second clock lines for at least a portion of the distance. The shield cage has a plurality of openings. The shield cage and/or shield wall may be connected to the ground of an AC power supply.