AFE Circuit Multiplexing for Variable-Gain Offset Cancellation
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Solution Overview
Problem
Existing sensor systems face challenges in canceling offset signals due to process mismatches between sensing units and readout circuit channels, especially when dealing with variable gains, as fixed compensation values are not effective in dynamically changing gain scenarios.
Innovation Solution
An analog front-end (AFE) circuit with multiplexers that selectively couple sensing units to multiple sensing circuits, allowing signals to be received and processed by different circuits in alternating time slots, thereby averaging out offset influences, and a gain amplifier with switchable configurations to achieve consistent gains across different settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed compensation values are used to cancel offset, then offset cancellation is achieved for fixed gain, but the compensation becomes ineffective when gain varies dynamically
Solution Approach 1:
The patent applies dynamics by making the compensation signal adaptive rather than fixed. The readout circuit dynamically adjusts the compensation signal based on the actual gain applied to the sensing signal, enabling effective offset cancellation across varying gain conditions. This transforms the static compensation approach into a dynamic one that responds to changing operational parameters.
Solution Approach 2:
The patent changes the parameter of the compensation signal from a fixed value to a variable value that depends on the gain parameter. By making the compensation signal's magnitude dependent on the gain setting, the system maintains effective offset cancellation across different gain levels. This parameter change allows the compensation mechanism to adapt to variable gain conditions.
2Measurement precision
If multiple sensing circuits are used to reduce offset, then offset cancellation improves, but circuit complexity increases
Solution Approach 1:
The patent merges the functions of multiple sensing circuits into a single shared circuit through time-division multiplexing. Instead of using multiple parallel sensing circuits simultaneously, the system alternates a single sensing circuit between different sensing units in different time slots, achieving offset reduction through temporal separation while maintaining hardware simplicity.
Solution Approach 2:
The patent employs periodic action by alternating the single sensing circuit between different sensing units in a time-division manner. The circuit periodically switches between servicing different sensing units, and this periodic alternation allows offset influences to be averaged out over time while using only one physical sensing circuit.
Data Source
AI summary
An analog front-end (AFE) circuit, configured to be coupled to a sensor having a plurality of sensing units, includes a plurality of sensing circuits and a plurality of multiplexers. Each of the plurality of multiplexers is coupled between one of the plurality of sensing units and at least two of the plurality of sensing circuits.