Self-Calibrating Intermediate Voltage Circuit for Uniform ADC References
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Solution Overview
Problem
Existing analog-to-digital converters, such as flash ADCs, face limitations in accuracy due to resistor matching issues, parasitic currents, and varying output impedance, leading to distortion and high power dissipation when generating uniformly spaced reference voltages.
Innovation Solution
A circuit and method utilizing an array of self-calibration units with error amplifiers, comparators, and digital-analog converters to generate intermediate voltages, where each unit adjusts its output to maintain uniform spacing, minimizing dependence on resistor properties and ensuring constant output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistor chain is used to generate linearly spaced voltages, then the voltage spacing is uniform, but the accuracy is limited by resistor matching and requires calibration
Solution Approach 1:
The patent implements self-calibrating voltage reference circuits that automatically adjust their output voltages to maintain precise spacing without external calibration. The circuit uses feedback mechanisms where each voltage reference unit monitors and adjusts its own output based on the voltages of neighboring units, eliminating the need for manual calibration while maintaining high accuracy.
Solution Approach 2:
The patent employs feedback loops in each voltage reference unit where the output voltage is continuously monitored and adjusted based on error signals. The feedback mechanism compares the actual voltage spacing against the desired spacing and automatically corrects deviations, ensuring high measurement precision without requiring external calibration equipment.
2Measurement precision
If small resistor values are chosen to reduce the impact of parasitic currents, then the voltage spacing remains uniform under load, but power dissipation increases
Solution Approach 1:
The patent replaces the passive resistor chain with active voltage reference circuits that use transistors and operational amplifiers to generate and regulate voltages. This substitution allows the circuit to maintain stable voltage spacing under load conditions without relying on small resistor values, thereby reducing power dissipation while preserving measurement precision.
Solution Approach 2:
Each voltage reference unit in the patent automatically adjusts its output to maintain precise spacing regardless of parasitic currents or loading conditions. The self-regulating nature of the active circuits eliminates the need to minimize resistor values, allowing the use of larger resistors with lower power consumption while maintaining voltage spacing stability.
3Device complexity
If a resistor chain is used to generate reference voltages, then the circuit is simple, but the output impedance varies across different taps causing distortion at high frequencies
Solution Approach 1:
The patent implements individual voltage reference units, each with its own output impedance control circuitry. This allows each tap to maintain a consistent output impedance independently, ensuring uniform frequency response across all voltage references. The local quality principle enables each unit to be optimized for consistent performance rather than relying on the global simplicity of a passive resistor chain.
Solution Approach 2:
The patent replaces the passive resistor chain with active voltage reference circuits that can actively control and maintain consistent output impedance across all taps. This substitution introduces complexity but resolves the frequency response uniformity issue by enabling active impedance matching and compensation that passive resistors cannot provide.
4Measurement precision
If resistor matching is improved by increasing the geometrical size of resistors, then accuracy improves, but the device area increases
Solution Approach 1:
The patent replaces the reliance on large physical resistors for achieving good matching with active voltage reference circuits using transistors and operational amplifiers. These active components achieve superior voltage matching and precision without requiring large geometrical sizes, thereby reducing the overall device area while maintaining or improving measurement precision.
Solution Approach 2:
The patent changes the fundamental approach from passive resistor matching to active voltage regulation. By using feedback-controlled voltage reference units, the system achieves high precision through electrical parameter control rather than physical dimension scaling, allowing for compact implementation with improved accuracy.
Data Source
AI summary
A network for generating a set of intermediate voltages comprising two input ports for feeding two reference voltages. The intermediate voltages are generated by a number of self calibration units that correspond to the number of intermediate voltages to be generated. Each self calibration unit receives the voltages of the neighboring calibration units or the voltage of one neighboring calibration unit and one of the reference voltages.