Temperature Measurement Input Stage Offset Cancellation
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Solution Overview
Problem
Existing temperature and voltage measurement circuits face challenges in accurately measuring resistances across varying temperatures and voltages due to offset errors and semiconductor device mismatch, which affect the reliability and precision of performance guarantees in semiconductor devices.
Innovation Solution
A temperature-measurement system and voltage-measurement system are developed, utilizing a current-mode buffer with multiplexors and amplifiers to alternate polarities during measurements, allowing for offset cancellation and precise resistance ratio calculation, enabling accurate temperature and voltage determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional temperature measurement circuit is used, then the circuit can measure temperature based on thermistor resistance, but offset errors and semiconductor device mismatch reduce measurement precision
Solution Approach 1:
The patent performs offset characterization measurements during manufacturing before the device is deployed. The offset values are measured and stored in non-volatile memory, then subtracted from subsequent temperature measurements to compensate for systematic errors. This preliminary action eliminates offset errors that would otherwise degrade measurement precision and reliability.
Solution Approach 2:
The patent implements a feedback mechanism where the measured offset values are used to correct future measurements. The offset characterization data is fed back into the measurement algorithm, allowing the system to continuously compensate for device mismatch and improve measurement accuracy over time.
2Measurement precision
If offset cancellation techniques are implemented, then measurement accuracy improves, but device complexity increases due to additional circuit components
Solution Approach 1:
The patent combines the offset characterization functionality with the normal temperature measurement circuit. The same buffer, amplifier, and ADC components are used for both offset measurement and temperature measurement, eliminating the need for separate dedicated offset cancellation hardware. This merging approach maintains measurement accuracy while minimizing additional circuit complexity.
Solution Approach 2:
The measurement circuit is designed to perform multiple functions: it can measure offset characteristics during manufacturing and perform temperature measurements during operation using the same hardware components. The multiplexor allows the circuit to switch between different measurement modes, making the system universal and reducing overall device complexity.
3Adaptability or versatility
If resistance measurements are performed at varying temperatures, then the measurement system can operate across wide temperature ranges, but semiconductor device mismatch causes measurement inaccuracies
Solution Approach 1:
The patent performs preliminary offset characterization at different temperatures during manufacturing to capture temperature-dependent offset behavior. These pre-measured offset values are stored and used to correct resistance measurements across the entire operating temperature range, maintaining precision despite temperature variations and device mismatch.
Solution Approach 2:
The patent measures and compensates for offset parameters at multiple temperature points. By characterizing how offset values change with temperature and storing this information, the system can adapt to temperature variations and maintain measurement precision across wide operating ranges despite semiconductor device mismatch.
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
The systems achieve high accuracy in temperature and voltage measurement by canceling out offset errors and semiconductor device mismatch-induced inaccuracies, ensuring reliable performance across a wide temperature range and voltage variations.
Implementation Method 1
Devices known as thermistors are known to have a resistances that vary over temperature. Accordingly, some applications measure the resistance of a thermistor in order to track the approximate temperature at which a circuit is operating.
Data Source
AI summary
A temperature-measurement input stage may include a resistor, a thermistor, a first multiplexor, an amplifier, a second multiplexor, and an output stage. The first multiplexor may be configured to couple the resistor to a first amplifier input during a first multiplexor state, and couple the thermistor to the first amplifier input during a second multiplexor state. The amplifier may comprise the first amplifier input, a second amplifier input coupled to a voltage reference, and an amplifier output coupled to a feedback path. The second multiplexor may be configured to route a feedback current to the resistor during the first multiplexor state and route the feedback current to the thermistor during the second multiplexor state. The output stage may be configured to provide an output current based on the feedback current.