Mixed-Signal IC Shield Structure for Signal Isolation
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Solution Overview
Problem
Mixed signal circuits, such as those used in analog-to-digital conversion, face performance degradation due to the propagation of digital signals into analog channels, which affects the accuracy of signal processing in applications like X-ray imaging.
Innovation Solution
The implementation of shield structures over the digital and analog portions of the integrated circuit, connected to respective grounds, to prevent signal propagation between the two signal types, thereby segregating digital and analog signal processing regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If digital and analog signal processing are integrated on the same circuit, then device complexity is reduced and integration is improved, but digital signals propagate into analog channels causing signal interference and performance degradation
Solution Approach 1:
The circuit is divided into distinct digital and analog portions with separate contact pads and conductive traces. Shield structures are positioned between these segments to block electromagnetic interference while maintaining physical integration on the same substrate, thus achieving segmentation without sacrificing integration benefits
Solution Approach 2:
Shield structures serve as intermediary elements between digital and analog signal paths. These shields act as electromagnetic barriers that prevent direct interference while allowing both signal types to coexist on the same circuit, effectively mediating the interaction between conflicting signal domains
2Measurement precision
If shield structures are added to prevent signal propagation, then signal interference is reduced and measurement precision is improved, but device complexity and manufacturing complexity increase
Solution Approach 1:
The shield structures are merged with the substrate as an integrated feature rather than separate components. The shields are formed using the same fabrication processes as the conductive traces and contact pads, combining multiple functions (signal routing, shielding, structural support) into a unified circuit design that reduces overall device complexity
Solution Approach 2:
The conductive traces and contact pads serve dual functions: they route electrical signals and simultaneously provide electromagnetic shielding when positioned between digital and analog portions. This multi-functionality reduces the need for separate shield components, simplifying the overall device structure
3Reliability
If shield structures are implemented, then signal propagation between digital and analog portions is limited and reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The shields are combined with the conductive traces and contact pads into a single integrated circuit layer. This merging ensures that shielding elements are automatically positioned with the same precision as the signal routing elements, eliminating the need for separate positioning processes and reducing manufacturing precision requirements
Data Source
AI summary
In certain embodiments, a mixed signal integrated circuit is provided that includes both a digital portion and an analog portion. A shield is provided that overlays one of the digital portion or the analog portion of the mixed signal integrated circuit. The shield limits propagation of signals between the digital portion and the analog portion of the mixed signal integrated circuit.