Capacitive Differential Isolator Calibration for Impedance Mismatch
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Solution Overview
Problem
Impedance mismatches in capacitive differential isolators degrade noise and interference immunity, causing unintended differential signals to be transmitted alongside intended signals, which affects the performance and integrity of communication channels.
Innovation Solution
A calibration method and system that drives a common signal across the isolator's input terminals, measures output signal differences, and varies impedance elements between output and center-tap terminals to minimize mismatches, using a controller and mismatch detector to adjust resistances in the impedance network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If impedance elements are added to calibrate mismatch, then signal integrity is improved, but device complexity increases
Solution Approach 1:
The calibration function is segmented into separate controllable impedance elements (first and second controllable impedance elements) that can be independently adjusted. This allows precise calibration of each differential path separately, improving signal integrity while keeping each individual element relatively simple.
Solution Approach 2:
The calibration is performed as a preliminary action before normal operation. A calibration signal is applied first to measure impedance mismatches, then the controllable impedance elements are adjusted accordingly. This preliminary calibration ensures signal integrity is optimized before actual data transmission begins.
2Object-affected harmful factors
If calibration circuitry is added, then noise immunity is improved, but ease of operation worsens
Solution Approach 1:
The system performs self-calibration through the calibration circuitry that automatically measures impedance mismatches and adjusts the controllable impedance elements without requiring manual intervention. The calibration controller autonomously manages the calibration process, improving noise immunity while maintaining ease of operation through automation.
Solution Approach 2:
The calibration process uses feedback from measuring the differential output signal in response to a calibration input signal. The system continuously monitors impedance mismatches and adjusts the controllable impedance elements based on this feedback, optimizing noise immunity dynamically.
Data Source
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AI summary
Embodiments of the present disclosure may provide a method of calibrating an isolator system. The method may comprise the steps of driving a common signal to a pair of input terminals of the isolator system; measuring differences in signals at output terminals of the isolator system; and varying impedance of impedance elements connected between the output terminals and a center-tap terminal of the isolator system until a mismatch at the output terminals is minimized.