FSK Digital Isolator Circuit for Common-Mode Transient Immunity
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Solution Overview
Problem
Digital isolators face challenges in addressing high-frequency transients (common mode transients) that corrupt data transmission across isolation barriers, leading to performance degradation, increased power consumption, and susceptibility to glitches, especially due to ground potential differences between circuits.
Innovation Solution
The implementation of a digital isolator with a frequency-shift keying (FSK) demodulator and switched capacitor circuits that modulate and demodulate data signals using a carrier frequency, allowing continuous transmission and reducing the impact of common mode transients by filtering out low-frequency components, thereby enhancing immunity to common mode transients and improving power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric is implemented to block direct current between isolated circuit sections, then isolation is achieved, but high-frequency transients can still corrupt data transmission across the isolation barrier
Solution Approach 1:
The patent introduces an isolation barrier comprising capacitors and transformers as intermediary elements between isolated circuit sections. The capacitors block direct current while allowing high-frequency signal transmission, and the transformers provide galvanic isolation. This intermediary structure enables reliable data transmission across the isolation barrier without direct electrical connection, preventing high-frequency transient corruption while maintaining isolation effectiveness.
Solution Approach 2:
The patent replaces traditional mechanical or direct electrical connection-based isolation with electromagnetic field-based isolation using capacitors and transformers. Instead of physical separation that blocks all signal transmission, the invention uses electromagnetic coupling through the isolation barrier to transmit digital signals while maintaining electrical isolation, thus preventing transient corruption without sacrificing communication reliability.
2Reliability
If traditional isolation methods are used to block direct current, then circuit isolation is achieved, but power consumption increases and the system becomes susceptible to glitches
Solution Approach 1:
The patent employs periodic clock signals to drive the capacitive isolation barrier, creating time-varying electric fields that enable signal transmission while maintaining isolation. The periodic switching of capacitors synchronized with the clock signal allows data transmission during specific phases while blocking direct current during other phases, thereby reducing average power consumption compared to continuous isolation methods while maintaining reliable circuit isolation.
3Loss of information
If isolation barriers with capacitors or transformers are implemented, then digital signal transfer is enabled, but the system becomes vulnerable to common mode transients due to ground potential differences
Solution Approach 1:
The patent implements ground reference circuits that maintain equipotential conditions across the isolation barrier by actively managing ground potential differences. The system uses controlled impedance paths and reference voltage generation to ensure that both sides of the isolation barrier reference their signals to the same potential level, thereby canceling out common mode transients caused by ground potential differences and preventing data corruption during signal transfer.
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
This solution provides improved common mode transient immunity, reduces power consumption, and prevents lock-up in wrong states, enabling efficient data transfer with high CMTI performance and scalable operation across varying supply voltages.
Implementation Method 1
Each digital isolator makes use of an isolation barrier or an isolation element in order to transfer the digital signal, wherein the isolation barrier includes one or more capacitors or transformers
Implementation Method 2
the isolation barrier includes one or more capacitors or transformers
Implementation Method 3
The output circuit includes a frequency-shift keying (FSK) demodulator configured to detect a presence of the carrier signal in the modulated differential data signals
Data Source
AI summary
Several circuits and methods for transferring an input data signal in a digital isolator are disclosed. In an embodiment, the digital isolator includes an isolation element, input circuit, and output circuit. The isolation element includes at least one input node and at least one output node, the input circuit is electronically coupled to the input node and generates modulated differential data signals based on modulating the input data signal on a carrier signal. The input circuit operates using a first supply voltage with respect to a first ground. The output circuit is electronically coupled to the output node to receive the modulated differential data signals, operates using a second supply voltage with respect to a second ground and includes a frequency-shift keying demodulator configured to generate a demodulated data signal in response to detection of presence of the carrier signal. The output circuit further generates an output data signal.