Programmable Chopping AFE With Integrated AAF for Offset Control
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Solution Overview
Problem
Conventional analog signal processing circuits, particularly analog-to-digital converters (ADCs), face challenges with undesirable offset voltages and frequency components due to noise, which can lead to inaccurate digital output values and require additional filtering, increasing component cost and size when integrating chopping circuits with anti-aliasing filters.
Innovation Solution
An analog front-end (AFE) is designed to include both an anti-aliasing filter (AAF) and nested chopping circuits to reduce offset voltages, with dynamic switch elements reconfiguring the AAF to improve settling symmetry and bypass input resistance during chopping operations, and a masking circuit to correct unsettled data stream values, all integrated within a single chip for efficient signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chopping circuits are integrated with anti-aliasing filters to reduce offset voltages, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines the anti-aliasing filter and chopping circuits into a single integrated circuit structure. The filter section includes capacitors and switches that work together with the chopping circuits to simultaneously perform filtering and offset reduction functions, eliminating the need for separate discrete components and reducing overall system complexity.
Solution Approach 2:
The integrated circuit is designed to perform multiple functions: the filter section removes unwanted frequency components while the chopping circuits reduce offset voltages. The same circuit components serve dual purposes, with the filter capacitors also acting as charge storage elements during chopping operations, thereby reducing the number of required components.
2Ease of manufacture
If conventional ADC architecture with separate filter and chopping circuits is used, then ease of manufacture is maintained, but offset voltage reduction effectiveness deteriorates
Solution Approach 1:
The patent merges previously separate filter and chopping circuits into a unified integrated structure where components share common elements. The filter capacitors are also used as charge storage capacitors in the chopping circuit, and the same switches control both filtering and chopping operations, achieving effective offset reduction while maintaining manufacturing simplicity through integration.
3Device complexity
If off-chip components are used for anti-aliasing filter, then device complexity is reduced, but productivity decreases due to increased component count
Solution Approach 1:
The patent integrates the anti-aliasing filter completely on-chip with the chopping circuits and ADC core, eliminating the need for off-chip filter components. This integration reduces the total component count and interconnections while improving signal processing productivity by enabling coordinated operation of all circuit elements through shared control signals and common timing.
Data Source
AI summary
An integrated circuit can include an amplifier coupled to receive an analog input signal, an anti-aliasing filter (AAF) coupled to an output of the amplifier, a buffer circuit coupled to an output of the AAF, a sigma-delta modulator configured to generate a digital data stream in response to an output of the buffer, and a plurality of chopping circuits nested within one another, including a first pair of chopping circuits having at least the amplifier disposed therebetween and configured to remove offset in the analog input signal, and a second pair of chopping circuit having at least the first pair of chopping circuits disposed therebetween. The amplifier, AAF, sigma-delta modulator, and chopping circuits can be formed with the same integrated circuit substrate. Corresponding methods and systems are also disclosed.