Digital Harmonic Distortion Correction via Common-Mode Feedback
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Solution Overview
Problem
Electronic systems experience common mode and differential mode errors due to process manufacturing mismatches, leading to substantial distortions that existing methods like resistor trimming and chopping fail to adequately address, often introducing noise and requiring additional components.
Innovation Solution
Implement a system with current sources that symmetrically control current sinks and sources to equalize common mode inputs, using delta-sigma modulators and dynamic element matching networks to measure and adjust currents and voltages, ensuring consistent behavior during both active and inactive cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If resistor trimming is used to correct mismatches, then manufacturing precision is improved, but device complexity increases and additional components are required
Solution Approach 1:
The system uses the existing common mode feedback loop to automatically detect and correct differential mode errors caused by resistor mismatches. The controller monitors the feedback signal and dynamically adjusts current source outputs to compensate for mismatches without requiring external trimming components or manual adjustment mechanisms.
Solution Approach 2:
The controller dynamically changes the output current parameters of the current sources based on the feedback signal to compensate for resistor mismatches. By adjusting the current magnitude and timing, the system corrects the differential mode errors without physical component changes.
2Reliability
If chopping is used to correct common mode errors, then common mode rejection is improved, but noise is introduced and device complexity increases
Solution Approach 1:
The system employs a feedback mechanism where the loop filter continuously monitors the output and feeds back error signals to the controller. The controller uses this feedback to dynamically adjust the current sources, achieving common mode rejection without the need for chopping techniques that introduce noise.
Solution Approach 2:
The loop filter acts as an intermediary between the driver and the current sources, processing the feedback signal and providing corrected control signals. This intermediary approach allows for smooth error correction without the abrupt switching actions that cause noise in chopping-based systems.
3Manufacturing precision
If additional current sources are added to correct mismatches, then manufacturing precision is improved, but device complexity and loss of substance increase
Solution Approach 1:
The existing current sources are made multi-functional by having them perform both their primary drive function and the additional function of correcting resistor mismatches. The controller dynamically allocates the current sources between these functions based on real-time feedback, eliminating the need for dedicated correction current sources and reducing overall power consumption.
Solution Approach 2:
The system dynamically adjusts the operation of current sources based on real-time feedback conditions. The controller modulates the current sources' output to simultaneously achieve drive functionality and mismatch correction, optimizing power usage by only activating correction mechanisms when mismatches are detected.
Data Source
AI summary
A system for equalizing errors in common mode inputs due to mismatches, the system including a driver configured to provide a first voltage to a first bus and a second voltage to a second bus; a loop filter coupled to the first bus and to the second bus and configured to provide a feedback signal; a first current source configured to source or sink a constant current from the first bus and second bus; a second current source configured to source or sink a variable current from the first bus and second bus; and a controller configured to receive the feedback signal, based on the feedback signal, determine a first value for the variable current, and responsive to determining the first value, control the second current source to source or sink the variable current having the first value.