Receiver Feedback Circuit for Common-Mode Offset and Crosstalk
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Solution Overview
Problem
Single-ended signaling in semiconductor devices experiences noise, jitter, and crosstalk due to parasitic inductors and adjacent signal line interference, which reduces the sensing margin of receivers handling CML level signals, necessitating effective cancellation of common mode offset and crosstalk to maintain data invariance.
Innovation Solution
A receiver circuit comprising amplifier circuits, equalizer circuits, and control circuits that amplify voltage differences, generate feedback signals, and adjust voltage levels using switching elements and control signals to cancel common mode offset and crosstalk, ensuring accurate signal conversion from CML to CMOS levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If single-ended signaling is used to reduce the number of signal pins and lines, then the circuit area is reduced, but noise, jitter, and crosstalk increase due to parasitic inductors and adjacent signal line interference
Solution Approach 1:
The patent implements feedback circuits that sense the common mode voltage level and generate compensating signals to cancel out the common mode offset and crosstalk. The feedback mechanism continuously monitors and adjusts the signal levels to maintain data invariance despite the presence of noise and interference in single-ended signaling.
Solution Approach 2:
The patent introduces equalizer circuits as intermediary components between the signal source and receiver. These equalizer circuits actively compensate for signal degradation, common mode offset, and crosstalk by generating corrective signals that restore the original signal integrity.
2Area of stationary object
If single-ended signaling is used to reduce circuit area, then the number of signal lines is reduced, but the sensing margin of the receiver decreases due to signal degradation
Solution Approach 1:
Feedback circuits monitor the received signal quality and adjust the common mode voltage level dynamically. By sensing the actual signal conditions and providing real-time compensation, the feedback mechanism maintains adequate sensing margin even in degraded single-ended signaling environments.
Solution Approach 2:
The patent dynamically adjusts voltage levels and signal parameters through equalizer circuits. By changing the common mode voltage and signal amplitude parameters adaptively, the system compensates for signal degradation and maintains sufficient sensing margin for reliable reception.
3Reliability
If common mode offset and crosstalk are present in the input signal, then data invariance deteriorates, but the receiver must still accurately determine logic levels
Solution Approach 1:
The feedback circuits detect common mode offset and generate compensating signals that are subtracted from the received signal. This feedback-based cancellation mechanism restores data invariance by removing the offset components that would otherwise corrupt the logic level determination.
Solution Approach 2:
The patent extracts and separates the common mode offset component from the differential signal using equalizer circuits. By isolating and removing the harmful common mode voltage and crosstalk components, the system recovers the clean differential signal necessary for accurate logic level determination.
Data Source
AI summary
A receiver for cancelling common mode offset and crosstalk that amplifies a voltage difference between an input signal and a reference voltage to generate first and second output signals and an internal signal, that generates the same third and fourth output signals as the first and second output signals, generates average voltage levels of the third and fourth output signals by using first and second switching elements and low pass filters to output the average voltage levels as first and second feedback signals, and cancels a common mode offset between the first output signal and the second output signal based on a voltage difference between the first feedback signal and the second feedback signal, and that generates a control signal to cancel crosstalk of the internal signal by turning on/off the first and second switching elements connected to the low pass filters.