Half-Cross-Coupled Decoupling Capacitor for High-Frequency Area Efficiency
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Solution Overview
Problem
Conventional decoupling capacitor designs face a trade-off between high operational frequency and high area efficiency, particularly in ultra-deep sub-micron and finFET process nodes, where they are susceptible to electro-static discharge (ESD) damage and struggle to maintain robust electrical properties.
Innovation Solution
A decoupling capacitor circuit design utilizing a half-cross-coupled configuration of p-channel and n-channel field effect transistors, supplemented with area efficient capacitance devices, allows independent setting of operating frequency and area efficiency, thereby eliminating the trade-off between frequency and area efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional DCAP designs use larger capacitive structures to maintain decoupling effectiveness at high frequencies, then operational frequency is improved, but area efficiency deteriorates
Solution Approach 1:
The decoupling capacitor is segmented into two distinct functional components: a first capacitive structure dedicated to high-frequency decoupling and a second capacitive structure dedicated to low-frequency decoupling. This segmentation allows each structure to be optimized for its specific frequency range, enabling the high-frequency structure to remain compact while the low-frequency structure handles the bulk decoupling requirements, thereby resolving the area efficiency problem at high operational frequencies
Solution Approach 2:
The patent introduces a frequency dimension to the capacitive design by operating the decoupling network across multiple frequency bands simultaneously. The first capacitive structure operates primarily in the high-frequency range while the second operates in the low-frequency range, effectively adding a frequency-based dimensionality that allows compact high-frequency performance without sacrificing overall decoupling effectiveness
2Area of moving object
If conventional DCAP designs reduce capacitor area to improve area efficiency, then area efficiency is improved, but decoupling effectiveness at high frequencies deteriorates
Solution Approach 1:
By segmenting the decoupling function into frequency-specific capacitive structures, the patent ensures that high-frequency decoupling effectiveness is maintained through the first capacitive structure optimized for that range, while the second capacitive structure provides adequate low-frequency decoupling. This segmentation prevents the loss of decoupling effectiveness that would occur if a single reduced-size capacitor were used across all frequencies
Solution Approach 2:
Each capacitive structure is designed with local quality optimized for its specific frequency range. The first capacitive structure has characteristics (such as lower ESR and ESL) tailored for high-frequency operation, while the second is optimized for low-frequency operation. This localized optimization ensures that decoupling effectiveness is maintained in each frequency band without requiring excessive area in either structure
3Device complexity
If single capacitive structure designs are used to simplify the circuit, then device complexity is reduced, but the ability to address both high-frequency and low-frequency decoupling requirements simultaneously deteriorates
Solution Approach 1:
The decoupling network is segmented into multiple capacitive structures, each with distinct electrical characteristics and frequency response profiles. This segmentation enables the circuit to simultaneously address both high-frequency and low-frequency decoupling requirements, providing adaptability across a broad frequency spectrum while maintaining a relatively simple overall architecture that integrates naturally with standard CMOS processes
4Reliability
If larger capacitive structures are used to maintain decoupling effectiveness, then decoupling effectiveness is improved, but power consumption increases
Solution Approach 1:
By segmenting the decoupling function into frequency-specific structures, the patent enables each capacitive element to operate within its optimal efficiency range. The first capacitive structure handles high-frequency transient currents with low ESR, while the second handles low-frequency decoupling, thereby maintaining overall decoupling effectiveness without the excessive power consumption that would result from using a single large-capacitance structure across all frequencies
Data Source
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AI summary
A decoupling capacitor circuit design facilitates high operational frequency without sacrificing area efficiency. In order to disassociate the sometimes opposing design criteria of high operational frequency and area efficiency, a p-channel field effect transistor (PFET 302) and an n-channel field effect transistor (NFET 304) are connected in a half-cross-coupled (HCC) fashion. The HCC circuit is then supplemented by at least one area efficient capacitance (AEC) device in the form of a second NFET (802) or a second PFET (702). The half-cross-coupled transistors address the high frequency design requirement, while the AEC device(s) address the high area efficiency requirement. The design eliminates the undesirable trade-off between operating frequency and area efficiency inherent in some conventional DCAP designs.