Programmable ELDC Gain in SAR Delta-Sigma ADC Quantizers
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Solution Overview
Problem
Continuous-time delta-sigma ADCs using successive approximation register (SAR) quantizers face slow conversion due to their successive nature, necessitating excess loop delay compensation (ELDC) to address the conversion delay, which complicates gain programming and calibration.
Innovation Solution
Incorporating a charge pump with digitally programmable capacitance into the ELDC circuit to adjust the gain of either the ELDC DAC or the SAR DAC, allowing for efficient programming and calibration of the ELDC gain, enabling flexible and precise compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a SAR ADC is used as a quantizer in a delta-sigma ADC to reduce power, then power consumption is reduced, but conversion speed becomes slow due to the successive nature of SAR conversion
Solution Approach 1:
The patent divides the conversion process into two parallel paths: a fast path that handles excess loop delay compensation using a separate DAC, and a successive approximation path that performs precise quantization. This segmentation allows the SAR ADC to operate at lower power while the ELDC path compensates for speed limitations.
Solution Approach 2:
The patent introduces an intermediary ELDC DAC that mediates between the slow SAR conversion process and the fast delta-sigma modulation requirement. The ELDC DAC compensates for the delay introduced by SAR's successive approximation, enabling the low-power SAR ADC to meet timing requirements.
2Speed
If ELDC DACs are added to compensate for SAR conversion delay, then conversion speed is improved, but device complexity increases
Solution Approach 1:
The patent merges the ELDC DAC capacitor array with the SAR DAC capacitor array, allowing both functions to share the same physical capacitors. This merging reduces the total component count and circuit complexity while maintaining both ELDC and SAR functionality.
Solution Approach 2:
The patent makes the capacitor array universal by enabling it to serve dual purposes: functioning as the ELDC DAC for delay compensation and as the SAR DAC for precise quantization. This multi-functionality eliminates the need for separate dedicated components for each function.
3Measurement precision
If ELDC gain programming is implemented to compensate for conversion delay, then conversion accuracy is improved, but ease of operation deteriorates due to complicated programming and calibration
Solution Approach 1:
The patent implements self-calibration functionality where the system automatically determines and adjusts the ELDC gain without requiring manual intervention. The calibration process is triggered automatically and uses built-in test signals to measure and compensate for delays, making the system self-sufficient.
Solution Approach 2:
The patent incorporates feedback mechanisms during calibration where the system measures the actual conversion results and uses this information to adjust the ELDC gain programmable capacitors. This closed-loop feedback ensures accurate compensation while simplifying operation through automatic adjustment.
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
This approach enhances the tuning range and precision of the ELDC gain, improving the efficiency and accuracy of the SAR-based quantizer in delta-sigma ADCs, supporting applications where ELD gain changes dynamically and allowing self-calibration.
Implementation Method 1
a charge pump coupled to either the first set of capacitors or the second set of capacitors, the charge pump having a programmable capacitance to adjust a gain
Data Source
AI summary
An excess loop delay compensation (ELDC) technique for use with a successive approximation register (SAR) based quantizer in a continuous time delta-sigma ADC is described. The techniques can efficiently program and calibrate the ELD gain in ELD compensation SAR quantizers. An ELDC circuit can include a charge pump having a digitally programmable capacitance to adjust a gain, such as the gain of the ELDC digital-to-analog converter (DAC) or the gain of the SAR DAC.