External Chopper Sensor Circuit for Low-Offset ΣΔ Conversion
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Solution Overview
Problem
Existing sigma-delta analog-to-digital converters (ΣΔ-ADCs) for chopped sensors face challenges in reducing offsets, noise, and loop complexity.
Innovation Solution
A sensor circuit is proposed with an analog chopper circuit external to the ΣΔ-modulator, shifting the analog input signal to a chopping frequency, and a digital chopper circuit external to the ΣΔ-modulator, demodulating the digital signal to restore the original frequency component. This configuration eliminates chopper circuits within the ΣΔ-modulator, allowing for a non-chopped ΣΔ-ADC design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chopper circuits are integrated within the ΣΔ-modulator to cancel offset voltages and low frequency errors, then offset errors and drift are reduced, but device complexity and loop complexity increase
Solution Approach 1:
The patent divides the chopper function into two separate circuits: an analog chopper circuit before the ΣΔ-modulator for modulation, and a digital chopper circuit after the modulator for demodulation. This segmentation removes chopper circuits from within the ΣΔ-modulator loop, reducing loop complexity while maintaining offset cancellation capability through the external analog and digital chopper circuits
Solution Approach 2:
The patent extracts the chopper circuits from the ΣΔ-modulator loop and places them externally. The analog chopper circuit is positioned before the modulator input, and the digital chopper circuit is positioned after the modulator output, thereby eliminating internal chopper complexity while preserving the offset cancellation function
2Object-affected harmful factors
If chopper circuits are used to shift signal to chopping frequency, then low frequency noise is reduced, but device complexity increases
Solution Approach 1:
The patent replaces traditional analog chopper circuits within the ΣΔ-modulator with a combination of external analog modulation and digital demodulation. The analog chopper circuit modulates the input signal to chopping frequency, and the digital chopper circuit demodulates the output, substituting complex internal analog chopping with a simpler external analog-digital hybrid approach that reduces overall circuit complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution achieves low offset, low noise, and reduced loop complexity by effectively shifting and demodulating the signal components, allowing signal components at the chopping frequency and its harmonics to pass through the ΣΔ-modulator, thereby enhancing the wideband character of the ADC.
Implementation Method 1
an analog chopper circuit configured to shift an analog input signal from an original frequency to a chopping frequency to generate a chopped analog signal
Implementation Method 2
a digital chopper circuit coupled to an output of the ΣΔ-modulator and configured to demodulate the chopped digital signal to generate a demodulated chopped digital signal having a signal component at the original frequency
Data Source
AI summary
The present disclosure relates to a sensor circuit including an analog chopper circuit configured to shift an analog input signal from an original frequency to a chopping frequency to generate a chopped analog signal, a ΣΔ-modulator coupled to an output of the analog chopper circuit and configured to digitize the chopped analog signal at a sampling frequency to generate a chopped digital signal, and a digital chopper circuit coupled to an output of the ΣΔ-modulator and configured to demodulate the chopped digital signal to generate a demodulated chopped digital signal having a signal component at the original frequency.