PTAT Current Reference Temperature Sensing Circuitry
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Solution Overview
Problem
Existing temperature sensing methods in implantable medical devices, such as thermistors, face challenges in accuracy, power consumption, and mechanical reliability, requiring complex calibration and increasing the size and vulnerability of the devices.
Innovation Solution
A temperature sensing circuitry that uses a Ptat current reference stage with resistances set based on desired temperature thresholds, generating analog signals indicative of temperature and threshold voltages, which are then processed to produce digital signals for temperature threshold detection, reducing power consumption and eliminating the need for discrete thermistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermistors are used for temperature sensing, then temperature measurement is achieved, but device complexity and manufacturing complexity increase due to calibration requirements
Solution Approach 1:
The temperature sensing circuit performs self-calibration by utilizing internal circuit components (transistors, resistors, diodes) that inherently exhibit temperature-dependent characteristics. The circuit automatically determines its own temperature without requiring external calibration procedures or discrete thermistor components, thereby eliminating manufacturing complexity while maintaining measurement accuracy.
Solution Approach 2:
The invention extracts the temperature sensing function from discrete thermistor components and integrates it directly into the circuitry using standard semiconductor components. This eliminates the need for separate thermistor calibration processes and reduces device complexity by incorporating temperature sensing capabilities directly into the existing circuit architecture.
2Measurement precision
If discrete thermistors are used, then temperature sensing is provided, but device size increases and mechanical reliability decreases
Solution Approach 1:
The temperature sensing function is merged with the existing circuit components (transistors, resistors, diodes) rather than using separate discrete thermistor components. This integration eliminates mechanical connection points and reduces the number of discrete parts, thereby improving mechanical reliability while maintaining temperature sensing capability.
Solution Approach 2:
The invention replaces mechanical temperature sensing components (discrete thermistors requiring physical mounting and wiring) with an electronic implementation using semiconductor components. This substitution eliminates mechanical reliability issues associated with discrete component mounting and connections while providing integrated temperature sensing within the circuit board.
3Measurement precision
If thermistor-based temperature sensing is used, then temperature monitoring is achieved, but power consumption increases
Solution Approach 1:
The circuit uses its own operational components (transistors, resistors, diodes) to sense temperature, leveraging the natural temperature-dependent characteristics of these components. This self-service approach eliminates the need for separate powered thermistor sensors, thereby reducing overall power consumption while maintaining continuous temperature monitoring capability.
Solution Approach 2:
The existing circuit components serve dual functions: their primary function in signal processing/power delivery and their temperature sensing function. By making these components multi-functional, the invention eliminates the need for dedicated temperature sensing components that would consume additional power, thereby reducing total power consumption while maintaining monitoring capability.
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
Enables continuous temperature monitoring with high accuracy (+/−1°C) and reduced power draw (500 nA), simplifying manufacturing and reducing mechanical vulnerability, while allowing for precise control of device operations based on temperature thresholds.
Implementation Method 1
temperature sensing circuitry that uses a Ptat current reference stage with resistances set based on desired temperature thresholds, generating analog signals indicative of temperature
Data Source
AI summary
Temperature sensing circuitry for an Implantable Medical Device (IMD) is disclosed that can be integrated into integrated circuitry in the IMD and draws very little power, thus enabling continuous temperature monitoring without undue battery depletion. Temperature sensor and threshold setting circuitry produces analog voltage signals indicative of a sensed temperature and at least one temperature threshold. Such circuitry employs a Ptat current reference stage and additional stages, which stages contains resistances that are set based on the desired temperature threshold(s) and to set the voltage range of the sensed temperature. These analog voltages are received at temperature threshold detection circuitry, which produces digital signal(s) indicating whether the sensed temperature has passed the temperature threshold(s). The digital signal(s) are then provided to digital circuitry in the IMD, where they can be stored as a function of time for later review, or used to immediately to control IMD operation.