Digital Isolator Using Differential Signaling for Noise Immunity
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Solution Overview
Problem
Digital isolators face issues with square wave signals having low frequencies and being susceptible to noise due to large attenuation during transmission, particularly when dealing with signals between different voltage domains.
Innovation Solution
A digital isolator design featuring a pair of transceiver circuits and a control circuit, where each transceiver operates in either transmitting or receiving mode, utilizing DC isolation circuits and feedback voltage dividers to generate and compare differential signals, thereby enhancing signal transmission and reducing noise impact through differential signal transmission technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an on-off keying modulation scheme is used in digital isolators, then the output oscillating signal has a relatively high frequency that passes through the isolation circuit easily, but the input square wave signal has a relatively low frequency and is easily affected by noise due to large attenuation during transmission
Solution Approach 1:
The patent changes the signal transmission parameters by using differential signaling instead of single-ended signaling. The transmitting circuit generates complementary differential signals (positive and negative square wave signals) that maintain higher frequency characteristics through the isolation barrier, while the differential comparison circuit at the receiving end reconstructs the original low-frequency square wave signal with improved noise immunity.
Solution Approach 2:
The patent introduces an intermediary differential signaling mechanism between the transmitting and receiving circuits. The DC isolation circuit transfers differential signals across the isolation barrier, acting as an intermediary that preserves signal integrity while blocking noise and voltage differences. The feedback voltage divider circuits further mediate the signal levels to ensure proper operation.
2Adaptability or versatility
If a single transceiver circuit is used, then the device structure is simpler, but the signal transmission direction cannot be adjusted according to user needs
Solution Approach 1:
The patent implements multi-functionality by designing each transceiver circuit to operate in either transmitting mode or receiving mode based on control signals. The control circuit configures the first transceiver circuit as transmitting and the second as receiving, or vice versa, allowing the same hardware structure to serve multiple functions and adapt to different transmission direction requirements.
Solution Approach 2:
The patent introduces dynamic configurability through the control circuit that can switch the operational mode of each transceiver circuit. The transceiver circuits can dynamically change their function (transmitting or receiving) based on user needs, making the device adaptable to different application scenarios without requiring additional hardware.
3Reliability
If additional DC isolation circuits are added to increase voltage difference between domains, then the isolation capability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the DC isolation circuit functionality directly into the transceiver circuit structure. Instead of adding separate external DC isolation circuits, the isolation capability is integrated into the transmitting and receiving circuits themselves, which simplifies the manufacturing process while maintaining strong voltage domain isolation capability through the differential signaling architecture.
Data Source
AI summary
A digital isolator provided includes a pair of transceiver circuits and a control circuit. Each transceiver circuit includes a transmitter circuit, a receiver circuit, and a DC isolation circuit. When the control circuit controls one of the pair of transceiver circuits to operate in a transmitting mode and the other of the pair of transceiver circuits to operate in a receiving mode, the transmitting circuit of the transceiver circuit operating in the transmitting mode receives a square wave signal to generate a pair of differential square wave signals, the connected DC isolation circuits receive the pair of differential square wave signals to generate a pair of differential coupling signals, and the transceiver circuit operating in the receiving mode uses the pair of differential coupling signals to output the square wave signal through the design of a pair of feedback voltage divider circuits and a differential comparison circuit included therein.