Embedded Residue Amplifier Offset Tracking in Pipelined ADCs
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Solution Overview
Problem
Multi-stage Analog-to-Digital Converters (ADCs) face challenges in accurately correcting offset errors in residue amplifiers, which can lead to reliability issues due to amplified offset voltages exceeding the redundancy range, especially under environmental changes and aging, requiring a real-time offset correction mechanism.
Innovation Solution
A discrete-time offset-compensation circuit is embedded in the residue amplifier, utilizing a low-pass filter and amplifier to detect and correct offset voltages by storing the offset on a capacitor and applying it to the residue amplifier's input, effectively canceling out the offset during ADC conversions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-stage ADCs are used to achieve high precision and high sampling speed, then conversion accuracy is improved, but offset voltage drift exceeds redundancy range causing reliability issues
Solution Approach 1:
The patent implements a feedback mechanism where the residue amplifier output is fed back through a low-pass filter to detect offset voltage, which is then corrected by adjusting the input to the residue amplifier. This closed-loop feedback system continuously monitors and compensates for offset drift, maintaining reliability while preserving the high precision benefits of multi-stage ADC architecture.
Solution Approach 2:
The offset correction circuit is self-regulating, automatically detecting and correcting its own offset voltage without external intervention. The low-pass filter and feedback path enable the system to self-diagnose offset drift and self-correct by adjusting the residue amplifier input, ensuring long-term reliability without adding complex external calibration equipment.
2Reliability
If real-time offset correction is implemented, then long-term reliability is improved, but circuit complexity increases
Solution Approach 1:
The offset correction functionality is merged with the existing residue amplifier circuit by embedding the low-pass filter and correction mechanism directly into the signal path. This integration approach achieves real-time offset correction without adding separate standalone correction circuits, thereby limiting the increase in overall device complexity while maintaining improved reliability.
Solution Approach 2:
The residue amplifier is designed to serve multiple functions: signal amplification, offset detection through feedback, and offset correction through input adjustment. This multi-functional design eliminates the need for dedicated offset correction hardware, achieving real-time reliability improvement with minimal additional circuit complexity.
3Power
If offset voltage is amplified by residue amplifier, then signal gain is improved, but offset error is magnified beyond correction range
Solution Approach 1:
The system performs preliminary offset detection and correction before the amplified offset error becomes too large. By continuously monitoring the residue amplifier output through the low-pass filter and preemptively adjusting the input to compensate for detected offset, the system prevents offset magnification from exceeding the correction range, maintaining both signal gain and error control.
Solution Approach 2:
The low-pass filter serves as an intermediary element that selectively passes offset voltage information to the feedback path while blocking amplified signal components. This intermediary allows the system to detect and correct offset errors without being overwhelmed by the magnified offset that results from high signal gain, effectively mediating between gain and error control.
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 solution significantly reduces offset voltage drift, allowing the ADC to track changes over time and conditions, improving long-term reliability and precision by compensating for offset errors in real-time during conversions.
Implementation Method 1
an offset detection and correction circuit including a low-pass filter
Implementation Method 2
an amplifier to amplify the filtered offset
Implementation Method 3
to generate an amplified filtered offset to drive onto a capacitor
Implementation Method 4
A discrete-time offset-compensation circuit is embedded in the residue amplifier, utilizing a low-pass filter and amplifier to detect and correct offset voltages by storing the offset on a capacitor and applying it to the residue amplifier's input, effectively canceling out the offset during ADC conversions.
Data Source
AI summary
A multi-stage pipelined Analog-to-Digital Converter (ADC) has an offset correction circuit embedded in the residue amplifier between stages. The offset corrector has a low-pass filter that filters the output of the residue amplifier, and the filtered offset is amplified and stored on an offset capacitor during an autozeroing phase of the residue amplifier. During an amplify phase of the residue amplifier, switches disconnect the amplifier from the offset capacitor and instead ground the input of the offset capacitor, and other switches connect the output terminal of the offset capacitor to the input of the residue amplifier. The offset stored on the offset capacitor is combined with the residue voltage from the first ADC stage's capacitor array and applied to an input of the residue amplifier to effectively subtract the detected offset. Two offset capacitors and sets of switches can be used to implement a differential offset corrector.