Auto-Zeroing Residue Amplifier for Low-Noise ADC Conversion
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Solution Overview
Problem
Existing analog-to-digital converters (ADCs) face challenges in achieving low-power, low-offset, and low-noise precision conversion due to non-zero offset drift and increased broadband noise in auto-zeroing (AZ) circuits, which are detrimental for applications requiring accurate and reliable signal conversion.
Innovation Solution
An analog-to-digital converter (ADC) circuit with an auto-zeroing residue amplification circuit that operates in two phases, combining two observations of an amplified residue value to cancel potentially non-zero offsets, thereby reducing noise and power consumption while maintaining signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If auto-zeroing circuits are used to stabilize offset, then offset stability is improved, but broadband noise increases
Solution Approach 1:
The amplifier operates in periodic phases: a first phase where the amplifier is disabled and offset is sampled, and a second phase where the amplifier is enabled and processes the signal. This periodic switching allows offset cancellation without continuous amplification, reducing broadband noise while maintaining offset stability.
Solution Approach 2:
The offset component is extracted and sampled separately during the first phase when the amplifier is disabled. By isolating and measuring the offset independently, it can be subtracted from the signal phase measurements, eliminating its harmful effect without requiring continuous amplification that would generate broadband noise.
2Measurement precision
If auto-zeroing circuits are used to reduce offset drift, then conversion accuracy is improved, but power consumption increases
Solution Approach 1:
The amplifier is enabled only during specific phases (signal processing phase) and disabled during other phases (offset sampling phase). This periodic operation reduces average power consumption compared to continuous operation, while still achieving offset cancellation to maintain conversion accuracy.
Solution Approach 2:
The offset is sampled and stored in advance during the first phase before the signal processing phase begins. This preliminary measurement of offset allows for accurate cancellation during signal processing without requiring the amplifier to remain continuously powered, reducing overall power consumption.
3Object-affected harmful factors
If continuous amplification is used to maintain signal level, then signal-to-noise ratio is improved, but offset drift increases
Solution Approach 1:
The amplifier is switched between disabled and enabled states periodically. During the disabled phase, offset drift is minimized. During the enabled phase, the signal is amplified with improved signal-to-noise ratio. The periodic re-sampling of offset compensates for any drift that occurs during signal processing.
Solution Approach 2:
The offset sampled during the first phase is used as feedback to cancel the offset during the second phase. This feedback mechanism continuously corrects for offset drift, allowing the amplifier to operate with improved signal-to-noise ratio without suffering from cumulative offset drift.
Data Source
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AI summary
Disclosed herein are some examples of analog-to-digital converters (ADCs) that can perform auto-zeroing with amplifying a signal for improvement of a signal-to-noise ratio. The ADCs may produce a first digital code to represent an analog input signal and a second digital code based on a residue from the first digital code, and may combine the first digital code and the second digital code to produce a digital output code to represent the analog input signal. The ADC may utilize a first observation and a second observation of an analog residue value representing the residue to produce the second digital code.