Differential Bus Receiver Switching for Symmetrical Level Detection
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Solution Overview
Problem
Existing receivers for differential data buses with two lines often experience level mismatches due to unequal voltage sources, leading to asymmetrical detection of positive and negative signal levels, which can result in high jitter.
Innovation Solution
A receiver design utilizing a single voltage source formed by a current source and a resistor, with a differential amplifier and control logic to switch the current between two branches, ensuring symmetrical detection of signal levels by adjusting the switch position based on output signals from operational amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two voltage sources are used for detecting positive and negative levels, then the detection function is complete, but level mismatches occur leading to asymmetrical detection and high jitter
Solution Approach 1:
The patent merges two separate voltage sources into a single voltage source that serves both positive and negative level detection. The single voltage source is switched between two branches of the differential amplifier, eliminating the mismatch problem inherent in using two independent voltage sources while maintaining complete detection functionality.
Solution Approach 2:
The patent introduces a switching mechanism that dynamically assigns the single voltage source to different branches based on the detection phase. The switch is controlled by detection logic that monitors output signals from operational amplifiers, enabling the voltage source to alternately serve positive and negative level detection needs.
2Reliability
If a single voltage source is used for both positive and negative level detection, then symmetry and low jitter are achieved, but the circuit requires switching mechanisms
Solution Approach 1:
The patent employs dynamic switching to manage the single voltage source, using a switch controlled by detection logic that monitors operational amplifier outputs. This dynamic approach enables one voltage source to fulfill multiple roles without requiring permanently dedicated voltage sources for each branch.
Solution Approach 2:
The single voltage source is designed to perform multiple functions by being switched between different branches. This universal voltage source can detect both positive and negative levels sequentially, reducing the total component count while maintaining detection symmetry.
3Adaptability or versatility
If two voltage sources are used, then independent detection of positive and negative levels is possible, but manufacturing variations cause unequal voltages and level mismatches
Solution Approach 1:
The patent combines two independent voltage sources into one shared voltage source to eliminate manufacturing variations that cause voltage inequality. By using a single source that is switched between branches, the system maintains independent detection capability while ensuring voltage equality.
Solution Approach 2:
The patent uses a single voltage source that is temporarily copied to different branches through switching, rather than having permanent copies in each branch. This approach ensures that both branches reference the exact same voltage potential at any given time, eliminating mismatches caused by manufacturing tolerances.
Data Source
AI summary
The invention relates to a receiver for a differential data bus with two resistive branches (1, 2, 3; 4, 5, 6), with a differential amplifier with two transistors (9, 10), with a resistor (13), and with a control logic (16) that controls a switch (15) with which a current from a current source (14) is switchable to either side of the resistor (13), which resistor couples the two transistors (9, 10), and with two operational amplifiers (17, 18) which are coupled to the two transistors (9,10) of the differential amplifier with opposite poles, in which receiver the control logic detects from the output signals of the two operational amplifiers (17,18) whether a “0” or a “1” is expected on the bus and which receiver sets the switch (25) accordingly so that a comparison with the received bus signal is made.