Kelvin-Contact Current Reference Circuit for Contact Drift
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Solution Overview
Problem
Conventional reference generators experience a 'resistor contact effect' due to deterioration of polysilicon resistor contacts, leading to variations in resistance, 1/f noise, and lifetime drift, which degrade the performance of voltage bandgap and current reference circuits.
Innovation Solution
A current reference circuit is designed with three resistors, each with four Kelvin contacts, allowing for force and sense measurements. This configuration makes the circuit insensitive to poor poly resistor contacts, reducing 1/f noise and lifetime drift by using sense voltage from Kelvin contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reference generators use polysilicon 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 segments the resistor contact structure into two independent parts: force contacts that carry the main current and sense contacts that measure the voltage. This segmentation allows the sense contacts to be positioned away from the deteriorating force contacts, eliminating the impact of contact resistance variations on the reference voltage while maintaining a relatively simple overall structure.
2Measurement precision
If Kelvin contacts are used for force and sense measurements, then the circuit becomes insensitive to poor poly resistor contacts, but the device complexity increases
Solution Approach 1:
The patent introduces sense contacts as intermediary elements that act as mediators between the force contacts and the measurement circuitry. These sense contacts provide a clean measurement path that is electrically isolated from the deteriorating force contacts, enabling precise voltage measurement without being affected by contact resistance variations.
3Stability of the object's composition
If sense voltage is taken from Kelvin contacts independent of force contacts, then contact resistance variations are eliminated, but the circuit complexity increases
Solution Approach 1:
The patent extracts the voltage measurement function from the force contact path by taking out the sense contacts and connecting them directly to the measurement circuitry. This extraction creates an independent measurement path that does not include the deteriorating force contacts, thereby eliminating their influence on the reference voltage stability while adding minimal circuit complexity.
Data Source
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.