Tunable Voltage Reference Circuit with Switched Capacitor Resistance
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Solution Overview
Problem
Existing precision voltage reference circuits are not adequately temperature- and radiation-stable, leading to errors in applications like guided vehicles and navigation systems, with current solutions being either bulky, noisy, or costly and sensitive to radiation.
Innovation Solution
A tunable switched capacitor resistance voltage reference circuit using a bridge circuit with a variable resistor and amplifier, where the resistance is tuned using a variable frequency control signal or variable capacitance to achieve stability, employing components like MOSFETs and varactors for temperature- and radiation-stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional precision voltage reference circuits are used, then voltage reference function is provided, but temperature stability and radiation stability are insufficient leading to errors in critical systems
Solution Approach 1:
The patent implements a dynamic tuning mechanism where a variable resistor (implemented as a switched capacitor) is controlled by a feedback loop to continuously adjust and maintain optimal resistance values. This dynamic adjustment compensates for temperature and radiation effects, achieving stability better than 1 ppm without requiring bulky mechanical apparatus
Solution Approach 2:
The patent employs a feedback control system where the voltage reference output is monitored and fed back to adjust the switched capacitor resistance. The feedback loop detects deviations caused by temperature or radiation and automatically corrects them by tuning the resistance, ensuring continuous high precision and stability
2Reliability
If mechanical apparatus or bulky circuits are used to achieve precision, then voltage reference stability is improved, but device size and complexity increase
Solution Approach 1:
The patent replaces traditional mechanical precision voltage reference apparatus with an electronic circuit implementation using switched capacitors and operational amplifiers. This substitution eliminates bulky mechanical components while achieving equivalent or superior precision through electronic tuning mechanisms, resulting in a compact integrated circuit design
Solution Approach 2:
The patent achieves precision voltage reference by dynamically changing the resistance parameter of the switched capacitor based on temperature and radiation conditions. Instead of using fixed-value components that require careful mechanical selection, the circuit electronically adjusts resistance values to maintain optimal performance, reducing device complexity
3Ease of manufacture
If bandgap reference circuits are used, then voltage reference function is provided, but noise and radiation sensitivity increase
Solution Approach 1:
The patent extracts and eliminates the noisy bandgap reference core from the circuit design. Instead of using forward-biased semiconductor p-n junctions that are inherently noisy and radiation-sensitive, the invention employs a switched capacitor-based reference that operates without these problematic components, thereby reducing noise and radiation sensitivity while maintaining ease of manufacture
Data Source
AI summary
A voltage reference circuit is provided. A voltage reference circuit includes a bridge circuit having a first branch, a second branch, and an amplifier. The bridge circuit is coupled between a precision voltage reference (PVR) node and a ground node. The first branch includes a first resistor of value R1 coupled to a reference resistor of value Rref at a first intermediate node. The second branch includes a second resistor of value R1 coupled to a variable resistor of value Rvar at a second intermediate node. Rvar is non-linearly tunable based on the PVR. The amplifier includes a positive input terminal coupled to the second intermediate node and a negative input terminal coupled to the first intermediate node. The amplifier is configured to generate the PVR.