Adaptive Common-Mode Noise Tuning in Differential Transmitters
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Solution Overview
Problem
Current methods for controlling common mode noise (CMN) in differential signals, such as using Common-Mode Chokes (CMC), increase manufacturing costs and can cause reliability issues due to overshoot and undershoot, and are static, not accounting for non-idealities in real product designs.
Innovation Solution
An adaptive CMN detection and decomposition technique that identifies root causes of CMN and tunes differential signal parameters like rise/fall-time, amplitude, and timing skew on-the-fly, eliminating the need for off-die CMCs and providing an on-die solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If Common-Mode Choke (CMC) is used to control CMN, then CMN suppression is improved, but manufacturing cost increases and reliability deteriorates due to overshoot and undershoot
Solution Approach 1:
The patent extracts the CMN control function from external components (CMC) and implements it within the IO buffer itself through on-die circuitry. The common mode voltage detector and tuning circuits are integrated into the transmitter, eliminating the need for external CMC components while maintaining CMN suppression capability.
Solution Approach 2:
The patent implements a feedback mechanism where the common mode voltage detector continuously monitors the common mode voltage level and feeds this information back to the tuning circuits. The controller adjusts differential signal parameters based on this feedback to dynamically suppress CMN without causing overshoot or undershoot issues associated with passive CMC components.
2Object-affected harmful factors
If Common-Mode Choke (CMC) is used to control CMN, then CMN suppression is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges the CMN detection and control functions with the existing IO buffer circuitry. The common mode voltage detector, tuning circuits, and controller are all integrated into the transmitter chip, combining multiple functions into a single integrated solution that eliminates external CMC components and reduces manufacturing cost.
Solution Approach 2:
The IO buffer performs self-diagnosis and self-adjustment by incorporating the common mode voltage detector and tuning circuits within the same device. The system automatically detects CMN issues and adjusts its own differential signal parameters without requiring external passive components like CMC, making the device self-sufficient and reducing manufacturing complexity.
3Device complexity
If static design control is used for CMN, then design simplicity is maintained, but adaptability to real product non-idealities deteriorates
Solution Approach 1:
The patent transforms the static CMN control approach into a dynamic one by implementing real-time monitoring and adjustment capabilities. The common mode voltage detector continuously monitors CMN levels, and the controller dynamically adjusts differential signal parameters (timing skew, rise/fall time, amplitude) based on actual operating conditions, enabling the system to adapt to various non-idealities in real products.
Solution Approach 2:
The patent employs parameter changes by adjusting multiple differential signal parameters (timing skew, rise/fall time, amplitude) through the tuning circuits. The controller modifies these parameters dynamically based on feedback from the common mode voltage detector, allowing the system to adapt to different operating conditions and non-idealities rather than relying on fixed static design values.
Data Source
AI summary
Described is an apparatus which comprises: a pre-driver coupled to a transmitter, the transmitter having a differential output; and a tuning circuit operable to couple to the differential output to tune the pre-driver of the transmitter according to a common mode noise signature of a common mode signal derived from the differential output.