Switched-Capacitor Front-End Gain Drift Compensation
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Solution Overview
Problem
Delta-sigma modulators in electronic circuits face gain drift due to temperature changes and environmental factors, which affect the performance of antialiasing filters loaded by switched capacitor circuits, leading to variations in signal gain.
Innovation Solution
A method and system that monitor changes in impedance of the antialiasing filter resistors relative to switched capacitors, using compensation circuitry to adjust the signal path and maintain consistent gain, employing environmental monitors and gain calculators to generate digital tuning signals for correcting gain errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a resistive antialiasing filter is directly loaded by a switched capacitor sampling front-end, then the filter can be implemented with simple circuit topology, but the filter gain varies due to environmental factors such as temperature changes
Solution Approach 1:
The patent implements a feedback mechanism by monitoring the impedance of the filter resistor and using this information to adjust the switched capacitor circuit. The system continuously tracks the resistor impedance changes due to temperature drift and applies compensating adjustments to the capacitor switches, thereby maintaining stable filter gain while keeping the overall circuit topology relatively simple.
Solution Approach 2:
The patent changes the operating parameters of the switched capacitor circuit based on monitored resistor impedance. By adjusting the effective capacitance or switching timing of the capacitor switches in response to measured impedance changes, the system compensates for temperature-induced gain variations without fundamentally altering the circuit architecture.
2Object-affected harmful factors
If the filter resistor value is increased to reduce loading effects, then the loading by switched capacitors is reduced, but the filter becomes more sensitive to environmental drift
Solution Approach 1:
The monitoring circuit continuously measures the actual impedance of the filter resistor and feeds this information back to the compensation circuitry. This feedback enables real-time detection of drift conditions, allowing the system to adjust the switched capacitor parameters to maintain stable gain regardless of the resistor value or loading conditions.
Solution Approach 2:
The system performs self-calibration by automatically monitoring its own impedance characteristics and adjusting its operation accordingly. The environmental monitor and gain calculator work autonomously to detect drift and apply corrections without external intervention, enabling the filter to self-correct for environmental variations.
3Productivity
If the switched capacitor equivalent resistance is decreased to increase sampling frequency or capacitance, then the sampling performance is improved, but the loading on the filter increases
Solution Approach 1:
The system monitors the interaction between the switched capacitor circuit and the filter by measuring resistor impedance changes. This feedback information is used to dynamically adjust the switched capacitor operation, compensating for the increased loading effect and maintaining stable filter performance even at higher sampling frequencies or with larger capacitance values.
Data Source
AI summary
A method may include, for a signal path comprising a passive antialiasing filter sampled by a switched-capacitor front-end, monitoring a change of a first impedance of a resistor of the passive antialiasing filter responsive to an environmental condition relative to a second impedance of a switched capacitor of the switched-capacitor front end and compensating the signal path for a change in gain of the signal path resulting from the change of the first impedance.