Delta-Sigma A/D Converter Feedback Matching for Temperature-Stable Accuracy
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Solution Overview
Problem
Continuous-time delta-sigma A/D converters face accuracy degradation due to temperature-dependent changes in voltage-current conversion coefficients, leading to deviations in compensation coefficients and reduced system accuracy.
Innovation Solution
Incorporating a compensation signal conversion circuit with a similar temperature-dependent conversion coefficient rate as the first signal conversion circuit, ensuring accurate loop delay compensation through a delta sigma A/D converter design with a loop delay compensation circuit and specific voltage-current conversion circuit configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous-time delta-sigma A/D converter is used to achieve lower power consumption and high-speed high-frequency signal processing, then power consumption is reduced and processing speed is improved, but accuracy degrades due to temperature-dependent changes in voltage-current conversion coefficients
Solution Approach 1:
The patent implements a feedback mechanism where the digital output signal is fed back through a D/A converter to the adder circuit, and a loop delay compensation circuit adjusts the feedback timing. This feedback loop continuously corrects for temperature-induced drift in conversion coefficients, maintaining accuracy despite environmental changes.
Solution Approach 2:
The patent changes the timing parameter of the feedback signal by introducing a loop delay compensation circuit that delays the feedback signal by a specific time period. This parameter adjustment compensates for the delay inherent in the quantizer and ensures accurate reconstruction despite temperature variations affecting conversion coefficients.
2Speed
If the sampling clock rate is increased to achieve high-speed processing, then processing speed is improved, but excess loop delay becomes significant and cannot be ignored
Solution Approach 1:
The patent applies preliminary action by pre-compensating for the loop delay before the feedback signal is used. The loop delay compensation circuit is designed to introduce a specific delay that counteracts the inherent delay in the quantizer, ensuring that the feedback timing is correct even at high sampling clock rates.
Solution Approach 2:
The loop delay compensation circuit acts as an intermediary element between the quantizer and the adder circuit. It mediates the timing relationship by introducing a controlled delay to the feedback signal, ensuring proper synchronization without requiring changes to the high-speed sampling clock rate.
3Ease of operation
If voltage-current conversion circuits are used in the feedback path, then signal processing is enabled, but conversion coefficient deviations occur due to temperature changes
Solution Approach 1:
The feedback mechanism continuously monitors and corrects for temperature-induced changes in conversion coefficients. By feeding the digital output back through the D/A converter and adder circuit, the system self-adjusts to maintain accurate conversion ratios despite temperature variations affecting the voltage-current conversion circuits.
Data Source
AI summary
An object of the present invention is to provide a highly accurate delta sigma A/D converter. Disclosed is a delta sigma A/D converter including: a first integration circuit to generate a first signal on the basis of an input signal and a first feedback signal from an output side; a first signal conversion circuit to convert the first signal into a first converted signal; a loop delay compensation circuit to generate a compensation signal and then to output the compensation signal in response to a second feedback signal fed back from the output side at a timing earlier than that of the first feedback signal; an adder circuit to add the first converted signal and the compensation signal; and a comparator to generate a digital signal on the basis of an output signal from the adder circuit. The loop delay compensation circuit includes a compensation signal conversion circuit to generate the compensation signal. The compensation signal conversion circuit and the first signal conversion circuit have the approximately same rate of change in conversion coefficient depending on a temperature.