Auto-Zeroing Residue Amplifier for Low-Noise Precision ADCs
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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 the inherent noise increase in auto-zeroing (AZ) circuits, which are necessary for stabilizing non-zero offsets but often consume more power to reduce noise to acceptable levels.
Innovation Solution
The implementation of an auto-zeroing residue amplification circuit that operates in two phases, amplifying and observing the residue value in both phases to combine the observations and cancel out the offset, thereby reducing noise and power consumption while maintaining precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If auto-zeroing circuits are used to stabilize offset, then offset stability is improved, but noise level increases and power consumption increases
Solution Approach 1:
The residue amplification circuit operates in periodic phases (first phase for auto-zeroing, second phase for signal amplification) rather than continuously. During the first phase, the circuit performs auto-zeroing to stabilize offset; during the second phase, it amplifies the residue signal. This periodic operation allows the circuit to achieve offset stability while reducing average noise and power consumption compared to continuous auto-zeroing operation.
2Measurement precision
If auto-zeroing circuits are used to stabilize offset, then offset stability is improved, but power consumption increases
Solution Approach 1:
The circuit implements periodic auto-zeroing operation where the residue amplification circuit alternates between auto-zeroing phase and signal amplification phase. This reduces average power consumption compared to continuous auto-zeroing while maintaining offset stability through regular calibration cycles.
Solution Approach 2:
The patent extracts the auto-zeroing function from continuous operation and confines it to specific phases. By separating the auto-zeroing operation from continuous signal processing, the circuit achieves offset stability only when needed, reducing overall power consumption while maintaining measurement precision.
3Object-affected harmful factors
If residue value is amplified in both phases, then signal-to-noise ratio is improved, but circuit complexity increases
Solution Approach 1:
The residue amplification circuit serves multiple functions: it performs auto-zeroing during the first phase and signal amplification during the second phase. By making the same circuit perform both functions at different times, the patent improves signal-to-noise ratio through consistent amplification in both phases while avoiding the need for separate dedicated circuits for each function, thus limiting the increase in overall circuit complexity.
Data Source
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.