Time-Multiplexed Resistor Matching for Temperature Sensing
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Solution Overview
Problem
In integrated circuits with smaller process geometries, the assumption of equivalent ratios of collector and emitter currents in p-n-p transistors leads to inaccurate temperature measurements due to variations in beta, causing errors in temperature sensing circuits.
Innovation Solution
A method of matching time-multiplexed resistors by switching them between series and parallel configurations to achieve a known resistance ratio, using a control signal to reconfigure resistors and account for variations, ensuring accurate current ratios and temperature measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the ratio of collector currents is assumed to be equivalent to the ratio of emitter currents in p-n-p transistors, then the temperature measurement can be simplified using the diode equation approximation, but the temperature measurement accuracy deteriorates due to beta variations in smaller process geometries
Solution Approach 1:
The patent changes the operating parameters by switching resistors between series and parallel configurations to dynamically adjust the current ratio. This allows the system to compensate for beta variations in smaller process geometries while maintaining simplified temperature measurement calculations, resolving the contradiction between measurement simplicity and accuracy.
Solution Approach 2:
The patent introduces dynamic switching of resistor configurations based on control signals, allowing the current ratio to be actively adjusted rather than fixed. This dynamic approach enables compensation for process geometry variations without requiring complex real-time measurements, balancing simplicity and accuracy.
2Device complexity
If time-multiplexed resistors are used to control collector current ratios, then the need for independent collector current measurements is eliminated, but resistor matching errors introduce additional inaccuracies
Solution Approach 1:
The patent merges multiple resistors into series and parallel configurations to create equivalent resistance values. By combining resistors rather than using single precision resistors, the system achieves better matching accuracy while eliminating the need for independent collector current measurements, resolving the contradiction between measurement simplicity and current ratio accuracy.
Solution Approach 2:
The patent segments the current control function across multiple resistors that can be independently switched between series and parallel configurations. This segmentation allows precise control of current ratios through configuration switching rather than requiring precise individual resistor values, improving current ratio accuracy without increasing measurement complexity.
3Measurement precision
If resistors are switched between series and parallel configurations to achieve known resistance ratios, then resistor matching is improved and current ratio accuracy is enhanced, but the device complexity and switching control requirements increase
Solution Approach 1:
The patent uses periodic switching of resistor configurations controlled by timing signals to achieve different current ratios at different times. This periodic action allows the same physical resistors to serve multiple functions sequentially, improving matching accuracy without requiring permanently complex circuitry for each configuration.
Solution Approach 2:
The patent makes the same set of resistors universal by switching them between series and parallel configurations to achieve different resistance ratios. This multi-functionality eliminates the need for separate resistor pairs for different current ratios, reducing overall device complexity while maintaining high matching accuracy through configuration switching.
Data Source
AI summary
An embodiment of the present invention is directed to a method of matching time-multiplexed resistors to a known ratio including generating a control signal from a control circuit, which includes a value that defines a configuration. The method also includes receiving the control signal at a switching circuit, detecting whether the value of the control signal has changed, and, provided the value has changed, switching a plurality of resistors from a first configuration to a second configuration. The first configuration produces a first resistance, and the second configuration produces a second resistance. The ratio of the first resistance and the second resistance are the aforementioned known ratio.