Hybrid Capacitor Inductor Digital Isolator for High CMTI
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Solution Overview
Problem
Current galvanic isolation methods, particularly silicon-based isolators, face challenges in achieving high Common Mode Transient Immunity (CMTI) due to sensitivity to parasitic capacitance and signal attenuation, leading to performance limitations and increased latency.
Innovation Solution
A hybrid capacitor and inductor based digital isolator circuit that employs a capacitive isolation barrier and a receiver LC tank with a center-tapped inductor pair, tuned to resonate with the transmitter, effectively cancels common mode signals without attenuating the signal of interest, improving signal-to-noise ratio and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitive isolation barrier is used for galvanic isolation, then electrical isolation is achieved, but signal attenuation and sensitivity to parasitic capacitance increase
Solution Approach 1:
The patent employs resonant oscillation at a specific frequency (typically 1-10 MHz) to transmit signals through the capacitive isolation barrier. By tuning the transmitter and receiver LC tanks to the same resonant frequency, signal transmission is maximized while parasitic capacitance effects are minimized, resolving the contradiction between isolation reliability and signal attenuation
Solution Approach 2:
The system dynamically adjusts operating parameters including resonant frequency, capacitance values, and inductance values to optimize signal transmission. By changing these parameters, the system maintains effective signal coupling across the isolation barrier while compensating for parasitic effects, thereby reducing signal attenuation
2Ease of manufacture
If conventional silicon-based isolators are used, then manufacturing compatibility is maintained, but Common Mode Transient Immunity performance is limited
Solution Approach 1:
The patent uses resonant LC tank circuits operating at specific frequencies to achieve high CMTI performance (exceeding 100 kV/µs). The resonant operation creates a high-impedance path for common mode transients while maintaining signal transmission, thereby improving CMTI without sacrificing CMOS manufacturing compatibility
Solution Approach 2:
The system combines capacitive and inductive elements (LC tanks) to create a hybrid isolation architecture that leverages the advantages of both approaches. This composite structure achieves high CMTI performance while remaining compatible with standard CMOS fabrication processes, resolving the contradiction between manufacturing ease and performance
3Reliability
If additional circuitry is added to cancel common mode signals, then CMTI performance improves, but device complexity increases
Solution Approach 1:
The patent converts the harmful effect of common mode transients into a beneficial filtering mechanism by using the resonant LC tank's natural frequency response. The resonant circuit inherently rejects common mode signals at frequencies other than the operating frequency, achieving CMTI performance without additional active cancellation circuitry
Solution Approach 2:
The LC tank circuits self-regulate to reject common mode transients through their resonant properties. The system uses its own operational characteristics (resonant frequency, Q-factor) to automatically filter out common mode interference, eliminating the need for external control circuits or additional complexity
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 hybrid approach enhances CMTI performance and reduces latency by canceling common mode transients without additional circuitry, while being less sensitive to losses and allowing implementation using standard CMOS processes and commercial silicon foundries.
Implementation Method 1
a receiver comprising a receiver inductor-capacitor (LC) tank; an oscillator tuned to a resonant frequency of the LC tank
Implementation Method 2
the receiver coupled inductor pair with a center tap is configured to cancel any common mode signal without attenuating the signal of interest
Data Source
AI summary
In general, one aspect disclosed features an apparatus comprising: a receiver comprising a receiver inductor-capacitor (LC) tank; a transmitter comprising an oscillator; and a capacitive isolation barrier electrically coupled between an output of the transmitter and an input of the receiver.