IC Temperature Sensor Offset Cancellation Using Swapped Comparator Inputs
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Solution Overview
Problem
Integrated circuits face reliability and robustness issues due to localized high temperature 'hot spots' caused by high switching events, and existing temperature sensing circuits using single slope ramp methods require fast clocks and are prone to offset errors from voltage buffers and comparators.
Innovation Solution
A temperature sensing circuit that uses twin first-order temperature-independent single slope ramp voltage references and counter circuitry, with switch circuits to swap inputs and outputs of buffers and comparators during measurement, effectively canceling offset errors by performing half the measurement with positive and half with negative offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single slope ramp method is used for temperature sensing, then the circuit can be implemented without requiring complex dual-slope architecture, but offset errors from voltage buffers and comparators cause significant measurement inaccuracies
Solution Approach 1:
The patent applies periodic action by alternating between two measurement phases: first measuring with the original buffer/comparator configuration, then swapping their positions and measuring again. This periodic swapping allows the offset errors to be captured in both phases, enabling their cancellation through differential calculation. The regular alternation between swapped and unswapped states creates a periodic measurement cycle that eliminates systematic offsets.
Solution Approach 2:
The patent converts the harmful offset errors from buffers and comparators into a beneficial cancellation mechanism. Instead of treating offset errors as unwanted disturbances to be eliminated through more complex circuitry, the invention deliberately measures and captures these offsets, then uses them to correct the final temperature measurement. The harmful offsets become useful correction terms that improve measurement accuracy.
2Ease of operation
If voltage buffers and comparators are used in the temperature sensing circuit, then signal conditioning and comparison functions are achieved, but inherent offset errors in these components introduce significant measurement errors
Solution Approach 1:
The patent implements feedback by using the measured offset values to correct the final temperature measurement. The offsets measured during the swapping phases are fed back into the calculation process, where they are subtracted from the raw temperature reading. This feedback mechanism continuously compensates for the buffer and comparator offsets, maintaining measurement accuracy despite the presence of these components.
Solution Approach 2:
The invention transforms the harmful offset errors introduced by buffers and comparators into useful correction information. By deliberately measuring these offsets through the swapping technique, the patent converts component imperfections into actionable data that improves the overall measurement accuracy. The offsets become beneficial correction terms rather than detrimental errors.
3Measurement precision
If offset cancellation through component swapping is implemented, then measurement accuracy is improved by reducing cumulative offset errors, but the measurement process requires additional switching operations and calculation steps
Solution Approach 1:
The patent manages the increased process complexity through periodic action by organizing the measurement into regular, repeating cycles. Each cycle consists of a fixed sequence: measure with original configuration, swap components, measure again, then revert to original configuration. This periodic structure makes the additional steps predictable and systematic, reducing the cognitive burden despite the increased number of operations.
Solution Approach 2:
The measurement system performs self-correction by automatically capturing and utilizing its own offset errors. The swapping mechanism causes the circuit to measure itself in two different states, and the differential calculation automatically eliminates the offsets without requiring external calibration or manual intervention. The system serves its own calibration needs through the inherent swapping operation.
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 approach improves the accuracy of temperature sensing by reducing cumulative offset errors, enhancing the reliability and robustness of integrated circuits by providing precise temperature measurements despite the presence of hot spots.
Implementation Method 1
uses a base-emitter voltage of a bipolar device and a single slope ramp based time-to-digital converter to provide precise temperature sensing
Data Source
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AI summary
Performing a temperature measurement operation includes a first phase and a second phase. The first phase includes providing a voltage indicative of a measured temperature to a first input of a comparator, providing a ramp signal to a second input of the comparator, and generating at an output of the comparator, pulses based on a comparison of the first input to the second input of the comparator. The second phase includes providing the voltage indicative of a measured temperature to the second input of the comparator, providing the ramp signal to the first input of the comparator, and generating at an output of the comparator, pulses based on a comparison of the first input to the second input of the comparator. Performing the temperature measurement operation also includes utilizing the pulses generated during the first and second phases to provide a digital indication of the measured temperature.