Inductance Delay Estimation for IC Timing Models
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Solution Overview
Problem
Calculating the effect of inductance on the time required for voltage propagation through integrated circuit interconnect wiring is complex, time-consuming, and often ignored, leading to inaccuracies as technologies advance and frequencies increase.
Innovation Solution
A method to quickly estimate inductance delay by determining the propagation delay of an electromagnetic field across a network of wires, using resistance-capacitance (RC) delays and total wire length, and adding the estimated inductance delay to the RC delay when appropriate, based on equations involving the speed of light in the chip dielectric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If detailed inductance extraction is performed using traditional methods, then measurement precision is improved, but productivity deteriorates due to the complex and time-consuming nature of the process
Solution Approach 1:
The patent uses a simplified inductance estimation model that provides adequate accuracy for timing analysis without requiring detailed inductance extraction. This approximate model is sufficient for the intended purpose and eliminates the need for complex, time-consuming traditional extraction methods, thus improving productivity while maintaining acceptable measurement precision
Solution Approach 2:
The patent changes the approach from exact inductance extraction to using an estimated inductance value derived from wire length and characteristic impedance parameters. This parameter substitution transforms a complex extraction problem into a simple calculation, resolving the contradiction between precision and productivity
2Productivity
If inductance effects are ignored to improve productivity, then extraction speed is improved, but measurement precision deteriorates leading to timing inaccuracies
Solution Approach 1:
The patent applies partial action by considering only the most significant inductance effects through a simplified model rather than performing complete inductance extraction. This partial approach maintains adequate timing accuracy for high-frequency circuits while preserving productivity by avoiding unnecessary computational complexity
3Measurement precision
If traditional inductance extraction methods are used, then measurement precision is improved, but device complexity increases due to the need for return paths and complex modeling
Solution Approach 1:
The patent extracts only the essential inductance effect from the complex traditional model by using a simplified estimation based on wire length and characteristic impedance. This extraction removes unnecessary complexity such as detailed return path modeling while retaining the critical inductance effect for timing analysis
Solution Approach 2:
The patent creates a simplified copy of the inductance effect through an estimation model that replicates the essential timing impact without requiring the full complexity of traditional inductance extraction. This copy approach maintains measurement precision while reducing device complexity
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
Provides a fast and approximate estimation of inductance effects on voltage propagation time, improving accuracy without the need for detailed inductance calculations, while avoiding inaccuracies that arise from ignoring inductance in high-frequency circuits.
Implementation Method 1
estimating an inductance delay of the network by determining a propagation delay of an electromagnetic (EM) field across wires of the network
Implementation Method 2
Calculating the effect of inductance on the time required to propagate voltage swings through the interconnect wiring of an integrated circuit
Data Source
AI summary
A method of estimating an inductance delay includes determining a resistance-capacitance (RC) delay with resistances and capacitances of a network and estimating an inductance delay of the network by determining a propagation delay of an electromagnetic (EM) field across wires of the network. Additionally, the method includes determining if the RC delay is below a specified threshold and adding the estimated inductance delay to the RC delay to determine a total time to propagate voltage swings through the network if the RC delay is below the specified threshold.