Bandgap Reference Compensation Using Oscillator-Based Resistor Tracking
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Solution Overview
Problem
Bandgap reference circuits face inaccuracies in reference voltage due to mechanical stress and temperature variations, which cause resistance changes in poly-resistors, leading to drift in the output voltage.
Innovation Solution
A bandgap reference correction circuit that includes a compensation module to detect frequency changes in an oscillator output signal and adjust the resistance of a first resistor based on these changes, using a reference frequency signal to maintain a constant reference voltage, with resistors of the same type and configuration to respond similarly to stress, and a temperature compensation circuit to manage temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If poly-resistors are used in bandgap reference circuits, then the circuit can be manufactured with standard processes, but the resistance changes due to mechanical stress and temperature variations cause reference voltage inaccuracies
Solution Approach 1:
The patent implements a feedback mechanism where an oscillator monitors the resistance of poly-resistors in real-time and automatically adjusts compensation resistors to counteract resistance changes. The compensation module continuously compares the oscillator frequency (which depends on resistor values) against a reference frequency and dynamically adjusts the compensation resistors to maintain accurate reference voltage, thereby resolving the contradiction between ease of manufacture and manufacturing precision.
Solution Approach 2:
The patent changes the resistance parameters of compensation resistors dynamically based on detected stress or temperature conditions. By adjusting the resistance values of compensation resistors in response to oscillator frequency shifts, the system compensates for poly-resistor drift and maintains reference voltage accuracy despite manufacturing variations and environmental changes.
2Reliability
If compensation circuits are added to correct resistance drift, then reference voltage stability is improved, but the circuit complexity increases
Solution Approach 1:
The patent merges the compensation function with the existing bandgap reference circuit by integrating the oscillator and compensation module into the reference voltage generation path. The compensation resistors are combined with the bandgap circuit components, and the oscillator is synchronized with the reference frequency, allowing a single integrated circuit to perform both reference generation and compensation functions, thereby improving reliability without proportionally increasing complexity.
Solution Approach 2:
The compensation circuit is designed to be self-regulating, where the oscillator automatically detects resistance changes and triggers the compensation module to adjust resistor values without external intervention. The system monitors its own performance through frequency comparison and autonomously corrects drift, reducing the need for external calibration or complex control mechanisms.
3Manufacturing precision
If resistors are placed close together on the semiconductor die, then matching and response to stress is improved, but the area occupied on the die increases
Solution Approach 1:
The patent applies local quality by creating a dedicated compensation region on the semiconductor die where compensation resistors are placed in close proximity to the bandgap reference circuit components. This localized arrangement ensures that compensation resistors experience the same mechanical stress and temperature conditions as the reference resistors, improving matching and compensation effectiveness while confining the area impact to a specific local region rather than spreading across the entire die.
Data Source
AI summary
A bandgap reference correction circuit comprising a bandgap reference circuit comprising a first resistor; a first oscillator comprising a second resistor, wherein a frequency of a first oscillator output signal of the first oscillator depends on a resistance of the second resistor; and a compensation module configured to: receive the first oscillator output signal from the first oscillator and a reference frequency signal from a reference oscillator; determine the frequency of the first oscillator output signal using the reference frequency signal; and set a resistance of the first resistor based on the frequency of the first oscillator output signal.