Resistor Network Single-Pass Trimming for Peak INL Reduction
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Solution Overview
Problem
Existing resistor string networks in digital-to-analog converters face challenges in achieving linearity due to manufacturing tolerances, requiring multiple pass trimming processes that are time-consuming and interactively complex, especially when driven by constant voltage sources.
Innovation Solution
A single-pass trimming method using discretely adjustable elements that trim all resistive structures to a same target value, minimizing Peak-INL by selecting trim codes that yield the minimum peak INL, reducing the number of necessary measurements and trim time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple pass trimming processes are used to improve linearity, then INL error is reduced, but trimming time and process complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating optimal trim codes through simulation before actual trimming. The method simulates all possible trim code combinations to identify the optimal code that minimizes INL error, then directly applies this pre-determined code in a single pass without iterative measurements, thereby reducing trimming time while maintaining precision
Solution Approach 2:
The patent uses copying by creating a simulated model of the resistor string network to predict trimming outcomes. Instead of repeatedly measuring and adjusting the actual network, the method copies the network's behavior in simulation to determine the optimal trim code, eliminating the need for multiple iterative measurements on the physical device
2Manufacturing precision
If multiple pass trimming processes are used to improve linearity, then INL error is reduced, but process complexity increases
Solution Approach 1:
The patent extracts the complex iterative measurement and adjustment process from the trimming operation. By separating the optimization calculation (performed once in simulation) from the execution (single pass trimming), the method eliminates the need for repeated measurements and complex control logic during actual trimming, significantly simplifying the process
Solution Approach 2:
The patent performs the complex optimization calculations in advance through simulation, extracting this complexity from the actual trimming process. The pre-calculated optimal trim code is then applied directly without requiring complex real-time control or iterative adjustments, thereby simplifying the manufacturing process
3Loss of time
If discretely adjustable elements are used with single pass trimming, then trimming time is reduced, but the ability to achieve optimal INL may be limited
Solution Approach 1:
The patent uses copying by simulating the discrete adjustable elements' behavior in a virtual model to evaluate all possible trim code combinations. This allows the method to identify the optimal trim code for discrete elements without requiring iterative physical adjustments, achieving both speed and precision
Solution Approach 2:
The patent applies preliminary action by pre-calculating the optimal trim code through comprehensive simulation of all discrete element combinations before actual trimming. This upfront calculation ensures that the single pass trimming achieves optimal INL performance despite the limitations of discrete adjustment steps
Data Source
AI summary
A single-pass method of trimming a network, and a network manufactured according to the method, uses the assumption that the peak INL value is minimized by trimming all the structures in the network to a same target value based upon the boundary conditions of the discretely adjustable elements that make up the structures. Using this assumption, the number of targets that need to be simulated, can be greatly reduced making estimation of peak INL possible in a reasonable amount of testing or manufacturing time. The trim algorithm produces results that are optimum or substantially close to optimum and is guaranteed not to deteriorate the Peak INL compared to the untrimmed Peak INL. An auto-calibration system using the trim method is also provided so that the method can be used in a product in real time if desired.