Shared DAC Calibration in Sigma-Delta Modulators for High Linearity
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Solution Overview
Problem
Multibit digital-to-analog converters in sigma-delta modulator circuits face challenges in achieving high linearity without increasing excess loop delay, chip area, and power consumption, especially when dynamic-element-matching techniques and self-calibration are used.
Innovation Solution
A shared calibration circuit is implemented between multiple multibit digital-to-analog converters, using a calibration input signal to select and control output cells for calibration during normal operation, thereby improving linearity without increasing excess loop delay or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dynamic element matching techniques are used to improve linearity of digital-to-analog converters, then linearity is improved, but excess loop delay of the sigma-delta modulator circuit increases
Solution Approach 1:
The calibration function is extracted from each individual digital-to-analog converter and placed in a separate shared calibration circuit. This allows the DACs to perform their primary conversion function without calibration-related delays, while the shared calibration circuit performs calibration operations independently, thus improving linearity without increasing excess loop delay.
Solution Approach 2:
A shared calibration circuit is introduced as an intermediary component that serves multiple DACs. This calibration circuit includes a calibration input for receiving calibration data and calibration output for providing calibrated signals to multiple DACs, enabling centralized calibration that reduces overall system delay while maintaining high linearity.
2Manufacturing precision
If self-calibrated digital-to-analog converters are provided to improve linearity, then linearity is improved, but chip area requirements increase
Solution Approach 1:
Multiple individual calibration circuits are merged into a single shared calibration circuit that serves all digital-to-analog converters in the multifeedback sigma-delta modulator. This shared calibration circuit includes a calibration input and calibration output that can service multiple DACs simultaneously or sequentially, significantly reducing the total chip area required for calibration functionality while maintaining high linearity across all converters.
3Manufacturing precision
If self-calibrated digital-to-analog converters are provided to improve linearity, then linearity is improved, but power consumption increases
Solution Approach 1:
Multiple power-consuming calibration functions are merged into a single shared calibration circuit. This shared calibration circuit performs calibration for all digital-to-analog converters using a single calibration input and calibration output, distributing the power consumption across the system rather than having each DAC consume power independently for its own calibration, thereby reducing total power consumption while maintaining high linearity.
Data Source
AI summary
In an integrated circuit including a first multibit digital-to-analog converter and a second multibit digital-to-analog converter, a calibration circuit is provided which is shared between the first and second digital-to-analog converters.