Sigma-Delta ADC Multiplexing with Filter State Restoration
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Solution Overview
Problem
Conventional sigma-delta modulators with digital filters face significant settling time delays when switching between input signals, making multiplexing inefficient due to the long time constants of digital filters, which leads to high power consumption and the need for multiple converters in multi-channel applications.
Innovation Solution
Implementing a sigma-delta converter that switches between digital filters and uses a sigma-delta modulator with a shorter settling time, discarding a small number of samples after switching, and resetting the modulator to minimize delay, allowing for efficient switching between input signals with reduced settling time and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital filters with large time constants are used for noise suppression in SD-converters, then measurement precision is improved, but switching time between input signals increases
Solution Approach 1:
The patent stores the internal state of the digital filter in a memory unit before switching input signals. When switching occurs, the stored state is reloaded into the filter, allowing it to resume processing without going through the complete settling period again. This preliminary storage of filter state enables rapid switching while maintaining noise suppression performance.
2Speed
If sampling frequency of SD-modulator and digital filter is increased to reduce settling time, then switching speed is improved, but power consumption increases
Solution Approach 1:
The patent changes the operational parameters of the digital filter dynamically based on the switching state. During normal operation, the filter runs at its designed sampling frequency for optimal noise suppression. When an input switch is detected, the filter state is preserved and the system quickly reloads it, avoiding the need to continuously increase the sampling frequency. This parameter adaptation allows fast switching without sustained high power consumption.
3Reliability
If one complete sigma-delta modulator and digital filter are provided for each channel, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements a single sigma-delta modulator and digital filter that can be dynamically assigned to serve multiple input channels. By storing the internal state of the filter in memory and能够快速 switching between channels with state restoration, one converter unit can reliably handle multiple channels sequentially, replacing the need for multiple dedicated converters and reducing overall system complexity.
Solution Approach 2:
The patent combines multiple channel processing capabilities into a single sigma-delta converter unit. By merging the functionality of what would traditionally require separate converters into one shared resource with stateful switching capability, the system achieves multi-channel support with reduced component count and lower complexity while maintaining conversion reliability.
Data Source
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AI summary
The present invention relates to an electronic device for analog-to-digital conversion including a sigma-delta modulator (SD), a digital filter (FIL) for digital post processing of the output signal of the sigma-deltamodulator (SD), a multiplexer (MUX) for switching the input (INSD) of the sigma-delta modulator between a first input signal (IN1) and a second input signal (IN2), amemory (MEM) adapted to hold the register content of the digital filter relating to the first input signal while the second input signal (IN2) is processed in the digital filter, and a controller (CNTL) to retrieve the register contents from thememory (MEM) when processing of the first input signal (IN1) in the digital filter is resumed.