ADC Comparator Offset Compensation Using Input Shuffling
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Solution Overview
Problem
Analog-to-digital converters (ADCs), particularly those using delta-sigma modulators, face challenges due to offset variation in comparators, leading to non-linear behavior and inefficiencies in high-speed, high-accuracy applications like analog and digital radio and radar systems.
Innovation Solution
A shuffler circuit is used to shuffle input sources to comparators in ADC circuitry, with feedback circuitry detecting and compensating for offset variations by providing auxiliary offset inputs based on average offsets, thereby removing offset differences and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a multibit topology is utilized to reduce sampling frequency and lower oversampling ratio, then sampling rate is reduced, but non-linear behavior is introduced due to mismatch and offset voltages in multi-bit elements
Solution Approach 1:
The system performs preliminary characterization of comparator offsets during an initialization phase before normal operation. Offset values are measured and stored in advance, then used to compensate for non-linearities during actual conversion operations, preventing rather than correcting the problem
Solution Approach 2:
The system implements feedback by using measured offset values from comparators to adjust subsequent conversion operations. The offset characterization results are fed back into the conversion process to compensate for non-linearities, creating a closed-loop system that improves linearity
2Device complexity
If offset variation in comparators is not compensated, then circuit simplicity is maintained, but non-linear behavior and measurement precision deteriorate
Solution Approach 1:
Offset characterization is performed in advance during an initialization phase, storing offset values in memory for later use. This preliminary measurement approach avoids the need for complex real-time compensation circuitry while maintaining high linearity
Solution Approach 2:
The patent introduces an intermediary characterization process that measures comparator offsets and uses these measurements to adjust the conversion process. This intermediary step separates the complex measurement function from the main conversion circuitry, keeping the primary path simple while achieving high precision
Data Source
AI summary
An apparatus including analog-to-digital conversion (ADC) circuitry is disclosed. The apparatus includes a plurality of comparators susceptible to offset variation and a shuffler circuit configured to shuffle input sources to the respective comparators. Feedback circuitry is also included and is configured and arranged with the ADC circuitry to detect offset variation in the outputs of each comparators for the shuffled inputs, relative to outputs of the plurality of comparators and compensate for the offset variation in the comparators based on the offset differences between the respective comparators.