Switch IC Layout Isolating Digital Control From RF Circuits
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Solution Overview
Problem
In high-frequency front-end circuits of mobile communication devices, the existing mixed integrated circuits face challenges in isolating digital control circuits from RF circuits, leading to interference and degradation of signal-to-noise ratio and receiving sensitivity due to the proximity of digital and RF lines.
Innovation Solution
The configuration surrounds the digital control circuit with high-frequency circuits and analog ground electrodes, physically spacing them apart to reduce digital noise interference, and uses a module substrate layout that isolates digital and analog lines, ensuring efficient isolation between digital control and high-frequency circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If digital control circuits and RF circuits are arranged in a mixed integrated circuit with digital circuits in a central portion, then it is possible to reduce coupling noise on lines, but isolation between digital and RF circuits is not ensured and interference of digital signals on RF lines occurs
Solution Approach 1:
The circuit is divided into distinct digital circuit regions and RF circuit regions, with the digital circuits positioned in a central portion and RF circuits arranged in peripheral portions. This spatial segmentation reduces coupling noise while maintaining isolation between the two circuit types through careful layout design and ground plane separation.
Solution Approach 2:
Ground planes are introduced as intermediary elements between the digital circuits and RF circuits. The ground planes act as shields that reduce electromagnetic coupling and interference between the digital and RF regions, enabling both circuits to coexist on the same substrate with reduced mutual interference.
2Device complexity
If RF circuits are arranged in a limited area from digital circuits, then integration is improved, but isolation between digital lines and RF lines is insufficient and digital noise degrades S/N ratio
Solution Approach 1:
Different regions of the substrate are assigned different functional qualities: the central region accommodates digital circuits with digital ground planes, while peripheral regions accommodate RF circuits with separate RF ground planes. This local differentiation ensures that each region has the appropriate grounding configuration to minimize interference with adjacent circuits.
Solution Approach 2:
The layout transitions from a simple planar arrangement to a three-dimensional structure utilizing multiple ground planes at different vertical levels. This vertical dimensionality allows for enhanced isolation between digital and RF circuits while maintaining compact integration on the substrate.
3Productivity
If baseband signal processing circuit is arranged adjacent to A/D and D/A converters, then signal processing efficiency is improved, but isolation from digital signals is reduced and interference occurs
Solution Approach 1:
Ground planes are positioned between the baseband signal processing circuit and the A/D and D/A converters to act as shields. This intermediary grounding structure reduces electromagnetic interference from the digital converters while still allowing the baseband circuit to efficiently process signals, achieving both isolation and functional efficiency.
Data Source
AI summary
An RF module includes a switch IC on a surface of a module substrate and a passive circuit provided in and/or on the module substrate. The switch IC includes a high-frequency circuit on an IC substrate and a digital control circuit. In a plan view of the IC substrate, the digital control circuit is surrounded by the high-frequency circuit. The high-frequency circuit includes analog ground electrodes in a boundary portion with the digital control circuit in the high-frequency circuit to surround the digital control circuit in the plan view.