Resistor Calibration Using MOS Capacitor Reference
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Solution Overview
Problem
Integrated circuit manufacturing technologies face challenges in achieving accurate resistor values due to temperature and process dependencies, resulting in ±15% dispersion, which increases manufacturing costs when higher accuracy is required.
Innovation Solution
A method and circuit that calibrate a variable resistor using a reference capacitor, where a constant current is directed through the capacitor and then the resistor, with a control signal adjusting the resistor until its voltage matches the capacitor's voltage, achieving an accuracy comparable to the capacitor's ±2% precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resistors are fabricated as polysilicon tracks with specified width and length to achieve desired resistance value, then the manufacturing process is simple and straightforward, but the resistance value accuracy deteriorates with ±15% dispersion due to temperature and process dependencies
Solution Approach 1:
The patent applies preliminary action by pre-calibrating the resistor value through a capacitor measurement before the resistor is put into service. The capacitor is measured during manufacturing when conditions are controlled, and this pre-obtained measurement is stored and used to adjust the resistor value later, compensating for process variations without requiring complex real-time measurement systems.
Solution Approach 2:
The patent uses a capacitor as an intermediary element to transfer the calibration information from the manufacturing process to the resistor. The capacitor serves as a mediator that captures the process variation signature during fabrication and allows this information to be used for resistor calibration, bridging the gap between manufacturing conditions and final resistor performance.
2Manufacturing precision
If post-fabrication trimming operations are performed to adjust individual resistors for better accuracy, then the resistance value accuracy improves, but the manufacturing cost increases
Solution Approach 1:
The patent implements self-service by enabling the resistor calibration system to automatically use the pre-measured capacitor values to adjust resistor values without requiring manual intervention or complex external measurement equipment. The system serves itself by utilizing already-available capacitor data to perform the calibration function, eliminating the need for expensive post-fabrication trimming operations.
3Measurement precision
If a MOS capacitor is used as a reference for resistor calibration, then the measurement precision improves to ±2% accuracy, but the device complexity increases due to additional calibration circuitry
Solution Approach 1:
The patent applies merging by combining the capacitor measurement function and resistor calibration function into a single integrated system. The same control logic and circuitry that measures the capacitor value during manufacturing is reused to perform the resistor calibration, eliminating the need for separate measurement and calibration systems and reducing overall device complexity despite the improved precision.
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 allows for accurate calibration of resistors to within ±2% accuracy, reducing manufacturing costs and improving resistor precision in integrated circuits.
Implementation Method 1
measuring a value of a reference capacitor
Implementation Method 2
adjusting a variable resistor based on the measured value of the reference capacitor
Implementation Method 3
varying the variable resistor value progressively by varying a control signal until a voltage of the variable resistor reaches a voltage of the reference capacitor
Data Source
AI summary
A method for calibrating a resistance value comprises the steps of measuring a value of a reference capacitor, and adjusting a variable resistor based on the measured value of the reference capacitor. The method may more specifically comprise the steps of directing a constant current through the reference capacitor during a reference time interval; after the reference time interval, directing the constant current through the variable resistor; and varying the variable resistor value progressively by varying a control signal until a voltage of the variable resistor reaches a voltage of the reference capacitor.