Resistor-String DAC Voltage Division for DNL Error Reduction
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Solution Overview
Problem
Digital-to-analog converters face challenges in achieving high accuracy and low cost with resolutions higher than 10 bits, particularly due to differential linearity errors caused by variations in unit resistor values in resistor string configurations, especially when resistors are bent, leading to increased conversion errors.
Innovation Solution
A resistor string digital-to-analog converter design that includes a high-order resistor string, first high-order switches, a high-order decoder, and a conversion unit, where the high-order switches are controlled to select voltage acquisition points that include a unit resistor with errors, allowing for error reduction through voltage division, thereby minimizing conversion errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If unit resistors are used in a resistor string configuration, then the digital-to-analog converter achieves high resolution and area reduction, but differential linearity errors increase due to variations in unit resistor values
Solution Approach 1:
The patent divides the resistor string into multiple segments with different numbers of unit resistors between adjacent voltage acquisition points. This segmentation allows the system to selectively use segments with fewer resistors (reducing cumulative error) while maintaining the required resolution through the overall structure design.
Solution Approach 2:
The patent implements non-uniform distribution of unit resistors across different segments of the resistor string. Specifically, adjacent voltage acquisition points are connected through different numbers of unit resistors, creating local variations in resistance that compensate for manufacturing tolerances and reduce differential linearity errors in critical measurement regions.
2Area of stationary object
If the resistor string is bent to fit layout constraints, then area efficiency is improved, but conversion errors increase due to stress-induced resistance variations
Solution Approach 1:
The patent segments the resistor string into multiple sections that can be independently routed and bent to fit layout constraints. By dividing the resistor string, the patent reduces the cumulative stress effect in each segment while maintaining the overall functionality, thereby reducing area without proportionally increasing conversion errors.
Solution Approach 2:
The patent applies different bending configurations to different segments of the resistor string based on local layout requirements. Critical segments with fewer unit resistors (which have lower error accumulation) are positioned in high-stress bent regions, while segments with more resistors are placed in lower-stress areas, optimizing the trade-off between area and accuracy.
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
The proposed solution effectively reduces conversion errors by voltage-dividing the errors present in unit resistors, maintaining high accuracy and area efficiency, even when resistors are bent, and achieving reduced differential linearity errors compared to conventional designs.
Implementation Method 1
a plurality of high-order analog voltages, which are obtained by dividing a first reference voltage and a second reference voltage with unit resistors
Implementation Method 2
The conduction state of the first high-order switches is controlled in accordance with a first high-order control signal
Implementation Method 3
The conversion unit outputs a voltage between a pair of analog voltage values, which are obtained through the pair of the first high-order switches, in accordance with a low-order control signal
Data Source
AI summary
A resistor string digital-to-analog converter includes a high-order resistor string, first high-order switches, a high-order decoder, a low-order decoder, and a conversion unit. The high-order resistor string includes a plurality of voltage acquisition points that are coupled through unit resistors. The high-order decoder generates a first high-order control signal in accordance with a high-order bit value, and operates in accordance with the first high-order control signal to bring into conduction a first high-order switch coupled to a pair of voltage acquisition points adjacent to each other through one or more voltage acquisition points. The low-order decoder generates a low-order control signal for controlling the conversion unit. The conversion unit divides a pair of high-order analog voltages output from a pair of voltage acquisition points.