USB Interface Module Level Shifting Across Ground-Offset Power Domains
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Solution Overview
Problem
Existing USB modules face challenges in communicating electrical signals due to significant ground voltage differences and ground loops, which can lead to incorrect signaling and limited amplitude of communicated signals, especially when using AC-coupling capacitors or transformers that block the DC component.
Innovation Solution
An integrated circuit with an interface module that includes a digital controller in a first power domain, an analog front end (AFE) circuit in a second power domain, and up/down level shifters to convey DC components between these domains without series capacitors, transformers, or opto-electric coupling, using buffers and voltage regulators to maintain signal integrity across power domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If AC-coupling capacitors are used to address ground-offset voltages, then the ground voltage difference is compensated, but the DC component of electrical signals is blocked
Solution Approach 1:
The patent extracts and removes the series capacitor from the signal path, eliminating the AC-coupling mechanism that blocks DC components. Instead, it uses separate ground voltage measurement and compensation circuits that do not interfere with the DC content of data signals, thereby preserving the full frequency spectrum including DC while still addressing ground offset issues.
Solution Approach 2:
The patent introduces intermediary circuits including dedicated ground voltage measurement circuits and compensation circuits that act as mediators between the host and peripheral ground domains. These intermediary circuits measure ground voltage differences and apply compensation without blocking the DC component of actual data signals, thus resolving the contradiction between ground offset compensation and DC signal preservation.
2Object-affected harmful factors
If transformers or opto-electric coupling are used to address ground loops, then ground loop interference is reduced, but the DC component of electrical signals is blocked
Solution Approach 1:
The patent removes transformers and opto-electric coupling components from the USB signal path. Instead, it uses direct electrical connections with separate ground voltage measurement and compensation mechanisms that preserve DC signal components while addressing ground loop interference through software-controlled voltage adjustments.
Solution Approach 2:
The patent replaces the mechanical/electromagnetic isolation mechanisms (transformers, opto-electric coupling) with an electronic/software-based ground voltage compensation system. This substitution uses digital control to adjust ground reference voltages dynamically, achieving ground loop mitigation without the signal blocking characteristics of traditional isolation methods.
3Object-affected harmful factors
If series capacitors are used for AC coupling, then ground-offset voltages are compensated, but the interface complexity increases and DC signals are blocked
Solution Approach 1:
The patent extracts and eliminates the series capacitor from the interface, simplifying the circuit topology. The ground offset compensation is achieved through separate measurement and compensation circuits that do not require AC coupling, thereby reducing interface complexity while preserving DC signal transmission capability.
Solution Approach 2:
The patent segments the ground voltage compensation function from the data signal path. By separating the ground voltage measurement, compensation control, and data transmission functions into distinct circuits, the system achieves ground offset compensation without requiring series capacitors, thus simplifying the overall interface while maintaining DC signal integrity.
4Object-affected harmful factors
If ground voltage compensation is implemented using traditional methods, then ground loops are addressed, but signal amplitude is limited due to leakage over ESD diodes
Solution Approach 1:
The patent applies local quality by implementing ground voltage measurement and compensation at specific localized points in the circuit rather than throughout the entire signal path. The compensation is applied locally to the ground reference without affecting the signal levels or causing leakage over ESD diodes, thus preserving full signal amplitude while addressing ground loop issues.
Solution Approach 2:
The patent introduces intermediary ground voltage measurement and compensation circuits that mediate between the ground domains without interfering with signal amplitude. These intermediary circuits provide ground reference adjustment without creating voltage drops or leakage paths that would limit signal strength, thereby maintaining full signal amplitude capability.
Data Source
AI summary
An integrated circuit is described. This integrated circuit may include: an interface module with a first power domain and a second power domain. The first power domain may include a digital controller, and the second power domain may include a first analog front end (AFE) circuit. Moreover, the interface module may include up/down level shifters that communicate electrical signals that include a DC component from the first power domain to the second power domain. In some embodiments, the integrated circuit may provide a fully on-chip solution to handle level shifting between the AFE circuit and a digital controller in Universal Serial Bus (USB) 2.0 during communication of electrical signals in a full-speed mode and/or a high-speed mode.