Polysilicon Resistor DAC Fine Tuning for Matching Accuracy
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Solution Overview
Problem
High-resolution Digital to Analog Converters (DACs) face challenges in achieving precise resistor matching due to process limitations, leading to inaccuracies and increased complexity, especially in segmented R-DAC architectures which require external buffers, increasing power consumption and noise.
Innovation Solution
The resistance value of each resistive element in a DAC is adjusted using electric fields applied to diffusion wells and metal plates, allowing for precise control of voltage coefficients, either during calibration or dynamically, to compensate for random mismatching and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If segmented R-DAC architecture is used to reduce the number of resistors, then device complexity is reduced, but manufacturing precision deteriorates due to process limitations in achieving well-matched resistors
Solution Approach 1:
The patent applies voltage coefficients to resistive elements to dynamically adjust their resistance values. By changing the voltage parameter applied to each resistor, the system compensates for manufacturing variations and achieves precise matching without requiring perfectly matched physical resistors, thus resolving the contradiction between reduced component count and manufacturing precision
Solution Approach 2:
The patent introduces dynamic adjustment capability through voltage-controlled resistance elements. The resistive elements can change their resistance values in real-time based on applied voltages, allowing the system to adapt and compensate for manufacturing imperfections, thereby maintaining high precision with fewer components
2Measurement precision
If external buffers are added to R2R ladder architecture to provide low impedance connections, then measurement precision is improved, but use of energy increases due to additional buffer power consumption
Solution Approach 1:
The patent combines the buffer function directly into the resistive element structure by integrating voltage control capability within the resistor itself. This merging eliminates the need for separate external buffer circuits, thereby maintaining output accuracy while reducing overall power consumption of the DAC system
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
This approach enables fine adjustment of resistive elements, reducing random mismatching and improving the overall accuracy of DACs, particularly in high-resolution applications, while minimizing the need for external buffers and reducing power consumption.
Implementation Method 1
The resistance value of each resistive circuit element is influenced by applying one or more electric fields to adjust a voltage coefficient
Implementation Method 2
a field oxide and/or Shallow Trench Isolation (STI) area can be used to provide a depletion region underneath an MOS gate structure... A voltage applied to with respect to gate terminal will appear on the channel across the gate (serving as the resistive element) oxide and allow for modulation of the resistance
Data Source
AI summary
A resistor string digital to analog converter formed of polysilicon resistor segments to each of which is applied an electric field. The approach improves the overall accuracy.