High Voltage FET Spiral Poly Resistor for Area-Efficient Drain Sensing
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Solution Overview
Problem
High voltage sensing in electronic circuits is challenging due to distorted voltage ratios caused by varying resistances in resistor segments, leading to inefficiencies in silicon area usage and pin count limitations in existing voltage sense methods.
Innovation Solution
A high voltage FET device with a spiral resistance poly structure over the drift region and taps on its outermost turn, where the innermost end is coupled to the drain electrode and the outermost end to a reference ground, providing a divided down sense voltage with reduced silicon area consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external discrete resistors are used for voltage sensing, then voltage sensing can be implemented, but silicon area consumption increases substantially
Solution Approach 1:
The voltage sensing function is merged with the existing drift region of the high voltage FET device. The spiral resistance poly structure is formed directly over the drift region, eliminating the need for separate external discrete resistors and their associated ESD structures, thereby substantially reducing silicon area consumption while maintaining voltage sensing capability
Solution Approach 2:
The drift region of the high voltage FET device serves multiple functions: it provides the high voltage blocking capability of the FET and simultaneously serves as the sensing element for voltage division. The spiral resistance poly structure formed over this region enables voltage sensing without requiring dedicated sensing components, achieving multi-functionality and reducing overall device complexity
2Device complexity
If diffusion resistors or poly resistors are used in integrated circuit, then voltage sensing is integrated, but voltage coefficient effect distorts voltage division ratio
Solution Approach 1:
The spiral resistance poly structure is specifically formed over the drift region where the electric field distribution is well-controlled and predictable. This localized placement ensures that the resistance values remain stable and accurate under high voltage conditions, minimizing the voltage coefficient effect and maintaining precise voltage division ratio without requiring each resistor segment to be in its own well tub
Solution Approach 2:
The spiral configuration of the resistance poly structure provides a distributed sensing approach where the curved path lengthens the effective sensing region while maintaining compact area. This spiral geometry helps distribute the voltage measurement across multiple points, reducing the impact of local voltage coefficient variations and improving overall measurement accuracy
3Measurement precision
If segmented resistors are used to minimize voltage coefficient effect, then measurement accuracy improves, but device complexity and pin count increase
Solution Approach 1:
Multiple resistor segments are merged into a single continuous spiral resistance poly structure formed over the drift region. This unified structure eliminates the need for multiple separate well tubs and complex interconnections, reducing device complexity and pin count while maintaining the distributed sensing benefits that minimize voltage coefficient effects
Data Source
AI summary
A high voltage FET device provides drain voltage information with less overall silicon area consumption by forming a spiral resistance poly structure over a drift region of the high voltage FET device. The spiral resistance poly structure has an inner most end coupled to a drain region, and an outer most end coupled to a reference ground.