Dual-Path Level Shifting for Low-Latency Ground Offset Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing signaling techniques face challenges in communicating electrical signals between power domains due to voltage offsets, which can result in signal loss or distortion, especially for low-frequency content, and often require active circuits that introduce latency, making them unsuitable for applications with low-latency requirements.
Innovation Solution
An integrated circuit with a level-shifting circuit that includes a switched-capacitor low-pass filter and a passive high-pass filter, allowing for selective frequency passage and minimal latency, enabling the transmission of low-frequency content, including DC, between power domains with different ground voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AC-coupling capacitor is used between power domains, then ground offset is addressed, but low-frequency content including DC is filtered out
Solution Approach 1:
The signal path is segmented into multiple parallel paths: an AC-coupling path for high-frequency content and a DC-coupling path for low-frequency content including DC. Each path handles specific frequency ranges, allowing both to coexist without interference. The segmented paths are then recombined at the receiver to reconstruct the complete signal.
Solution Approach 2:
A dual-path interface circuit acts as an intermediary between power domains with different ground offsets. The circuit includes parallel AC and DC coupling paths, each with appropriate level shifting, allowing signals to cross power domain boundaries while preserving both AC and DC components through selective routing and recombination.
2Reliability
If transformer is used between power domains, then ground offset is addressed, but low-frequency content cannot be propagated
Solution Approach 1:
The interface circuit segments the signal transmission into AC and DC coupling paths. The DC-coupling path uses direct connections with level shifters that can transmit low-frequency content including DC, while the AC-coupling path handles high-frequency content, replacing the transformer's frequency-dependent behavior with a broadband dual-path approach.
3Loss of information
If upconversion and downconversion are used, then low-frequency content is moved to higher frequencies, but propagation delay increases
Solution Approach 1:
The invention extracts the low-frequency and DC components from the signal and routes them through a dedicated DC-coupling path that bypasses the AC-coupling capacitor and associated upconversion/downconversion circuits. This direct path eliminates the propagation delay introduced by frequency conversion operations while preserving low-frequency content.
4Loss of information
If active circuits are used in signal path for upconversion, then low-frequency content is preserved, but latency increases
Solution Approach 1:
The signal path is segmented into passive AC-coupling and DC-coupling paths. The DC-coupling path uses passive components and level shifters instead of active upconversion circuits, thereby preserving low-frequency content while minimizing latency. Active circuits are confined to optional equalization functions rather than being required for basic signal transmission.
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
The solution allows for robust, low-latency communication of electrical signals with reduced distortion and higher bandwidth, suitable for applications like USB 2.0 modules, while simplifying the interface circuit and reducing power consumption, making it more reliable and cost-effective.
Implementation Method 1
a first filter that passes frequencies in the input electrical signal below a first corner frequency
Implementation Method 2
a second filter, in parallel with the first filter, that passes frequencies in the input electrical signal above a second corner frequency
Implementation Method 3
the switched-capacitor circuit may correct DC content in the input electrical signal for a difference between the first ground or reference voltage and the second ground or reference voltage
Data Source
AI summary
An interface circuit may convert an input electrical signal at an input node in a first power domain having a first ground or reference voltage into an output electrical signal at an output node in a second power domain having a second ground or reference voltage. Notably, a level-shifting circuit in the interface circuit may selectively electrically couple to the input node and the output node. Then, when there is electrical coupling, the level-shifting circuit may perform level shifting between the first power domain and the second power domain. The level shifting may involve: passing, using a first filter, frequencies in the input electrical signal below a first corner frequency; passing, using a second filter in parallel with the first filter, frequencies in the input electrical signal above a second corner frequency; and combining outputs of the first filter and the second filter as the output electrical signal.