TMR Bridge Offset Voltage Compensation via Resistor Cascades
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wheatstone bridges used in sensors, such as angle sensors, face significant offset voltage issues due to temperature coefficients, leading to performance degradation at temperatures different from the calibration temperature.
Innovation Solution
A TMR resistor cascade is used in conjunction with a bottom electrode resistor cascade, where the resistance values are adjusted using laser fuses or switches to compensate for bridge offset voltage and temperature coefficients, achieving a zero or near-zero temperature coefficient for the bridge offset voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If bridge offset voltage is calibrated on the chip, then manufacturing precision is improved, but temperature coefficient causes performance degradation at different temperatures
Solution Approach 1:
The patent introduces compensation resistors with opposite temperature coefficients to the bridge offset voltage. By selecting resistors whose temperature coefficients are opposite in sign to the bridge offset voltage's temperature coefficient, the system compensates for temperature-induced drift. The compensation amount is determined by the ratio of compensation resistor value to bridge resistor value, allowing precise adjustment of the compensation effect across different temperatures.
2Reliability
If temperature coefficient compensation is added, then reliability at different temperatures is improved, but device complexity increases
Solution Approach 1:
The patent combines the compensation resistors with the existing bridge circuit structure, integrating the temperature compensation function into the original sensor design. The compensation resistors are connected in parallel with the bridge resistors, merging the measurement and compensation functions into a unified circuit architecture rather than adding separate compensation circuits.
Solution Approach 2:
The patent achieves temperature compensation by carefully selecting resistor values and temperature coefficients. By adjusting the compensation resistor values relative to the bridge resistors, the system can compensate for temperature drift without requiring complex active compensation circuits, maintaining relatively simple device structure while improving reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively compensates for bridge offset voltage and temperature coefficients, ensuring optimal performance across varying temperatures by utilizing a combination of TMR and bottom electrode resistor cascades with opposing temperature coefficients, allowing for precise resistance adjustments.
Implementation Method 1
a combination of the TMR resistor cascade and a bottom electrode resistor cascade having opposing temperature coefficients may be used to result in an offset voltage compensation having a temperature coefficient of zero or substantially close to zero
Data Source
AI summary
A bridge circuit having a full-bridge circuit having a first branch and a second branch coupled in parallel, the first branch comprising a first half-bridge circuit and a first tunnel magnetoresistance (TMR) resistor cascade coupled in series, and the second branch comprising a second half-bridge circuit and a second TMR resistor cascade coupled in series, wherein the full-bridge circuit has an offset voltage of zero or substantially close to zero.