Kelvin Current Reference Circuit for Poly Resistor Contact Drift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional reference generators in integrated circuits are susceptible to the 'resistor contact effect' caused by polysilicon resistor contact deterioration, leading to variations in resistance, 1/f noise, and lifetime drift, which degrade performance.
Innovation Solution
A current reference circuit design utilizing a four-terminal Kelvin configuration with poly resistors, coupled with MOSFETs and BJTs, that isolates the sense contacts from the main current path, reducing the impact of contact variations and allowing for fine or course trim adjustments to maintain accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reference generators use poly resistors with standard contacts, then the circuit structure is simple, but the resistor contact deterioration causes variations in resistance, 1/f noise, and lifetime drift
Solution Approach 1:
The patent divides the resistor contact function into two separate contact structures: force contacts for current injection and sense contacts for voltage measurement. This segmentation allows the sense contacts to be positioned away from the deteriorating poly resistor contacts, eliminating the impact of contact resistance variations on the reference voltage while maintaining a relatively simple overall circuit structure.
2Reliability
If Kelvin contact configuration is used to eliminate contact effects, then contact resistance variations are eliminated, but the device complexity increases due to additional sense contacts and circuitry
Solution Approach 1:
The patent extracts the voltage sensing function from the current-carrying contacts by introducing separate sense contacts that draw negligible current. This allows the sense contacts to be placed at specific locations along the poly resistor where they can measure the reference voltage without being affected by contact resistance at the force contacts, thereby eliminating contact resistance variations while adding minimal complexity.
3Device complexity
If poly resistor contacts are used for both force and sense measurements, then the circuit is simpler, but contact deterioration leads to 1/f noise and lifetime drift
Solution Approach 1:
The patent introduces sense contacts as intermediary elements between the force contacts and the voltage measurement point. These sense contacts serve as mediators that transfer the reference voltage signal without being affected by the contact resistance and deterioration at the force contacts, thereby eliminating the generation of 1/f noise and lifetime drift while maintaining a simple contact configuration.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A current reference circuit, comprises a main resistor, comprising: a first force contact terminal at a first end of the main resistor and coupled to a first metal-oxide-semiconductor (MOS) component; a second force contact terminal at a second end of the main resistor and coupled to a second MOS component; a first sense contact terminal coupled to one bipolar junction transistor (BJT); and a second sense contact terminal opposite the first sense contact by a length of the main resistor and coupled to another bipolar junction transistor, wherein the first and second sense contact terminals exchange a current reference independently of the first and second force contact terminals.