Error-Feedback SAR ADC Buffer Using Shared Residue Capacitor
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Solution Overview
Problem
Noise-shaping successive-approximation-register analog to digital converters (SAR-ADCs) face challenges in achieving high accuracy while minimizing power consumption and size, as error-feedback structures increase complexity and power consumption.
Innovation Solution
The design incorporates an input sampling buffer with an amplifier and a gain-control capacitor that functions both in amplification and error-feedback configurations, allowing the same capacitor to be used for applying gain and receiving residue voltage, eliminating the need for additional capacitors and amplifiers, thus reducing area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If error-feedback structure is added to noise-shaping SAR-ADC, then accuracy is improved, but device size and power consumption increase
Solution Approach 1:
The gain-control capacitor is designed to perform multiple functions: it controls the gain of the input sampling buffer during normal operation and simultaneously serves as the feedback capacitor for receiving residue voltage during error-feedback operation. This multi-functionality eliminates the need for separate feedback capacitors and reduces overall device size while maintaining accuracy improvements from error-feedback noise-shaping.
Solution Approach 2:
The invention merges the gain-control function and residue feedback function into a single capacitor component. By combining these two previously separate functions into one shared capacitor, the overall device complexity and size are reduced while still achieving the accuracy benefits of error-feedback noise-shaping.
2Measurement precision
If error-feedback structure is added to noise-shaping SAR-ADC, then accuracy is improved, but power consumption increases
Solution Approach 1:
The gain-control capacitor performs dual functions as both gain control element and residue feedback storage element. This eliminates the need for additional dedicated feedback capacitors and their associated switching and control circuitry, thereby reducing overall power consumption while maintaining the accuracy improvements provided by error-feedback noise-shaping.
Solution Approach 2:
By merging the gain-control and residue-feedback functions into a single capacitor, the invention eliminates redundant circuit components and their associated power consumption. The shared capacitor approach reduces the total power required for capacitor charging, switching, and control operations.
3Measurement precision
If dedicated residue buffer and second amplifier are added for error-feedback, then noise-shaping performance is improved, but area consumption increases
Solution Approach 1:
The input sampling buffer's gain-control capacitor is made multi-functional by having it serve as both the gain control element and the residue feedback storage capacitor. This eliminates the need for a dedicated residue buffer and second amplifier, significantly reducing area consumption while maintaining noise-shaping performance through the shared capacitor's ability to perform both functions.
Solution Approach 2:
The invention extracts the residue feedback function from a separate dedicated buffer and amplifier structure and integrates it into the existing gain-control capacitor of the input sampling buffer. This extraction and integration approach eliminates redundant components and reduces overall area consumption.
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 enables efficient noise-shaping with increased accuracy without increasing power consumption, allowing for compact and low-power integrated circuit implementations while avoiding attenuation losses and complex calibration requirements.
Implementation Method 1
the gain-control capacitor connected in feedback with the amplifier, for applying gain to the analog signal sampled by the input sampling capacitor
Implementation Method 2
the gain-control capacitor... arranged to receive a residue voltage from the SAR-ADC
Data Source
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Figure 3
AI summary
Analog to digital conversion circuitry has an input sampling buffer (2), which has an input sampling capacitor (C1) for sampling an analog signal. The conversion circuitry also has a successive-approximation-register analog to digital converter (SAR-ADC) (3) which converts the sampled analog signal to a digital signal. The input sampling buffer (2) has an amplifier (8) and a gain-control capacitor (C2), and has an amplification configuration and an error-feedback configuration. In the amplification configuration, the input sampling capacitor (C1) is coupled to the amplifier (8) and gain-control capacitor (C2), with the gain-control capacitor (C2) connected in feedback with the amplifier (8), for applying gain to the sampled analog signal. In the error-feedback configuration, the gain-control capacitor (C2) is decoupled from the input sampling capacitor (C1) and receives a residue voltage from the SAR-ADC (3), such that the level of the analog signal determined in the amplification configuration varies depending on the residue voltage received onto the gain-control capacitor (C2) in the error-feedback configuration.