Sigma-Delta Modulator Reset Sequencing for Stable Startup
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Solution Overview
Problem
Incremental sigma-delta modulators face stability issues during startup due to large transients caused by constant inputs, which can destabilize the system and reduce signal-to-noise ratio (SNR) when attempting to mitigate this with gain settings.
Innovation Solution
The proposed solution involves a device with an input adder, integrators, an output adder, a quantizer, and a digital-to-analog converter, where the reset signals for the integrators are de-asserted at different times to manage the startup transient, preventing instability while maintaining SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If gain setting at the input is reduced to prevent instability, then stability is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies preliminary action by resetting the integrators in a specific sequence before normal operation begins. The first integrator is reset first, followed by downstream integrators, preparing the system in advance to handle large transient inputs without instability, thus avoiding the need for gain reduction while maintaining stability and signal-to-noise ratio.
Solution Approach 2:
The patent segments the reset operation into distinct phases for different integrators. Instead of a unified reset approach, the first integrator and downstream integrators are reset at different times, allowing controlled management of transient effects in each stage separately, resolving the contradiction between stability and signal-to-noise ratio.
2Productivity
If a large constant input is applied at power up, then the converter can process signals immediately, but instability occurs due to large step function at the input
Solution Approach 1:
The patent prepares the integrators in advance through sequential resetting before the large constant input is fully processed. By resetting the first integrator before downstream integrators, the system is pre-configured to handle the large input step function, enabling immediate signal processing without instability.
3Device complexity
If all integrators are reset at the same time, then the reset operation is simple, but instability occurs because feedback is at zero while input step function is large
Solution Approach 1:
The patent segments the reset operation into multiple phases, resetting the first integrator and downstream integrators at different times. This segmentation increases operational complexity slightly but resolves the stability issue by ensuring feedback is properly established before handling large input step functions.
Data Source
AI summary
A device and method for sigma-delta modulation may include an input signal and a plurality of integrators. The output of the integrators and a data input may be input to an adder, the sum output to be input to a quantizer to generate a quantized output signal. A reset input to the first integrator may be asserted during a first sample of the quantized output signal to reduce the signal discontinuity at the input of the first integrator, which improves the stability of the sigma-delta modulator.