Transverse Trimming Resistor Layout for Precision Resistance Tuning
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Solution Overview
Problem
High-precision resistors face challenges in achieving zero temperature coefficient of resistance (TCR) while maintaining accuracy and avoiding damage from high electrical trimming currents and voltages, especially when resistor geometry changes.
Innovation Solution
A high-precision resistor design featuring a transverse trimming resistor coupled to a functional resistor, allowing for precise electrical trimming without longitudinally traversing the functional resistor, thus avoiding voltage drops and enabling lower trimming voltages, with the trimming current and voltage determined by the trimming resistor's geometry rather than the functional resistor's.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high currents and voltages are applied to the functional resistor for trimming, then the desired resistance variation is achieved, but the resistor or device may be damaged
Solution Approach 1:
The resistor structure is segmented into two independent parts: a functional resistor for circuit operation and a trimming resistor for adjustment. The trimming resistor is traversed by trimming currents while the functional resistor is isolated, allowing precise resistance control without exposing the functional resistor to damaging high electrical quantities.
Solution Approach 2:
The trimming function is extracted from the functional resistor and implemented through a separate trimming resistor. This extraction allows the trimming operation to be performed on an independent element, eliminating the harmful effects of high trimming currents on the functional resistor while maintaining the ability to achieve desired resistance values.
2Ease of manufacture
If the trimming current depends on the functional resistor geometry, then trimming can be performed, but the method requires remodulation whenever geometry changes
Solution Approach 1:
By separating the trimming function into an independent trimming resistor, the trimming current requirements depend only on the trimming resistor's geometry, not the functional resistor's geometry. This segmentation provides universal trimming capability that remains consistent across different functional resistor designs.
Solution Approach 2:
The trimming resistor serves as a universal trimming element that can be used with various functional resistor geometries. The trimming method becomes geometry-independent, allowing the same trimming approach to be applied universally across different resistor designs without remodulation.
3Manufacturing precision
If laser trimming is used to obtain accurate resistance values, then precision is improved, but the system requires costly laser trimming apparatuses and complex interconnection levels
Solution Approach 1:
The patent replaces mechanical laser trimming with electrical trimming through current pulses. This substitution eliminates the need for costly laser trimming apparatuses and complex mechanical interconnection levels, while achieving comparable or superior precision through electrical control of the trimming resistor's resistance.
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 design allows for precise and safe trimming of high-precision resistors, reducing the risk of damage and power consumption, while enabling dynamic resistance modification during operation, with trimming voltages lower than traditional methods and independent of the functional resistor's geometry.
Implementation Method 1
dissipating electrical energy in a trimming resistor, transverse to the functional resistor
Data Source
AI summary
An embodiment of an electrically trimmable electronic device, wherein a resistor of electrically modifiable material is formed by a first generally strip-shaped portion and by a second generally strip-shaped portion, which extend transversely with respect to one another and are in direct electrical contact in a crossing area. The first and second portions have respective ends connected to own contact regions, coupled to a current pulse source and are made of the same material or of the same composition of materials starting from a same resistive layer of the material having electrically modifiable resistivity, for example, a phase-change material, such as a Ge—Sb—Te alloy, or polycrystalline silicon, or a metal material used for thin-film resistors. The trimming is performed by supplying a trimming current to the second portion so as to heat the crossing area and modify the resistivity thereof, without flowing longitudinally in the first portion.