Parallel Resistive Elements in LDMOS Voltage Dividers
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Solution Overview
Problem
In semiconductor devices, achieving high accuracy and repeatability of resistor ratios in voltage dividers is challenging, leading to inaccuracies in voltage measurement, particularly with large resistance ratios required in applications like power factor correction.
Innovation Solution
The use of two low voltage resistive elements connected in parallel within a voltage divider circuit, formed over the lateral diffusion area of an LDMOS transistor, with the resistive elements sharing the same manufacturing step and material, to stabilize and enhance the resistance value accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete resistors are used in voltage divider, then resistance accuracy can be very high, but device size becomes large and speed becomes slow
Solution Approach 1:
The patent replaces discrete mechanical/electronic resistors with resistors formed directly in the semiconductor device structure. Specifically, the invention uses the lateral diffusion area of an LDMOS transistor to form low voltage resistors, eliminating the need for separate discrete resistor components. This substitution enables smaller device size and faster operation while maintaining measurement precision through the integrated resistor design.
2Power
If large resistance ratio is used in voltage divider, then high voltage can be divided to manageable voltage, but resistance variability increases leading to measurement inaccuracies
Solution Approach 1:
The patent segments the low voltage resistor into multiple resistive elements connected in parallel. This segmentation approach allows the voltage divider to achieve the required large resistance ratio for high voltage division while reducing the variability of individual resistive elements. By using multiple parallel elements, the overall resistance accuracy improves, enabling precise voltage measurement even with large division ratios.
Solution Approach 2:
The patent merges multiple resistive elements in parallel to form the low voltage resistor. This combining approach reduces the total resistance variability compared to a single resistor, as the parallel configuration averages out variations in individual elements. The merged structure maintains the large resistance ratio needed for high voltage division while improving measurement precision.
3Device complexity
If single low voltage resistor is used, then device structure is simple, but resistance variability is high leading to poor repeatability
Solution Approach 1:
The patent segments the low voltage resistor into multiple identical or similar resistive elements formed in the same manufacturing step. This segmentation reduces resistance variability and improves repeatability because elements formed simultaneously in the same process exhibit better matching. The segmented structure achieves high reliability without significantly increasing device complexity, as the elements are integrated into the transistor fabrication process.
Data Source
AI summary
Described examples include a semiconductor device having a resistor. The resistor includes a first terminal and a second terminal. The resistor also includes a first resistive element over an insulating layer over a substrate having a first end coupled to the first terminal of the resistor and a second end coupled to the second terminal of the resistor; and a parallel second resistive element over the insulating layer over the substrate having a first end coupled to the first terminal of the resistor and a second end coupled to the second terminal of the resistor. The resistor may also be coupled in series with another resistor.