Diode-Connected Inverter Delay for Linear Thermal Sensing
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Solution Overview
Problem
Conventional thermal sensors, whether BJT-based, diode-based, or resistor-based, are either too large for small digital circuits or have poor output linearity and low temperature sensitivity, while digital thermal sensors like ring oscillators lack the necessary sensitivity for accurate temperature monitoring.
Innovation Solution
The design incorporates diode-connected transistors, specifically PMOS and NMOS transistors, in inverters and ring oscillators to create a thermal sensor with a propagation delay time that is a linear function of temperature, enabling accurate temperature monitoring through output frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional BJT-based, diode-based, or resistor-based thermal sensors are used, then temperature sensitivity is improved, but device area increases making them unsuitable for small digital circuits
Solution Approach 1:
The patent replaces conventional BJT-based, diode-based, or resistor-based thermal sensor structures with a CMOS-compatible inverter-based ring oscillator structure. This substitution enables temperature sensing using standard digital circuit components, achieving high temperature sensitivity while maintaining small device area suitable for integration in digital circuits.
Solution Approach 2:
The patent utilizes the temperature-dependent propagation delay parameter of the inverter circuit. By measuring changes in propagation delay time (which varies linearly with temperature), the system achieves high temperature sensitivity without requiring large sensor structures, thus resolving the contradiction between sensitivity and area.
2Area of moving object
If conventional ring oscillators are used as digital thermal sensors, then device area is reduced for small digital circuits, but temperature sensitivity and output linearity deteriorate
Solution Approach 1:
The patent introduces diode-connected transistors at specific locations within the inverter circuit to enhance the temperature sensitivity of the propagation delay. This localized modification improves the overall temperature sensing capability without significantly increasing device area, resolving the contradiction between small size and high sensitivity.
Solution Approach 2:
The patent exploits the temperature-dependent electrical characteristics of diode-connected transistors to create a propagation delay that is highly sensitive to temperature changes. By carefully designing the inverter circuit with these transistors, the system achieves linear temperature response with high sensitivity while maintaining compact dimensions suitable for digital circuit integration.
3Volume of moving object
If conventional ring oscillators are used, then device size is reduced, but output linearity and temperature sensitivity become poor
Solution Approach 1:
The patent modifies the electrical parameters of the inverter circuit by incorporating diode-connected transistors, which create a propagation delay time that is substantially linearly proportional to temperature. This parameter optimization achieves good output linearity while maintaining small device size, resolving the contradiction between compact dimensions and measurement accuracy.
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 provides high temperature sensitivity and linearity, making it suitable for small digital circuits with digital output, effectively addressing the limitations of existing thermal sensors by ensuring accurate temperature measurement with minimal size and power consumption.
Implementation Method 1
The propagation delay time of the inverter is substantially a linear function of the temperature of the inverter
Data Source
AI summary
The invention provides an inverter. The inverter includes a first converter and a second converter. The first converter is coupled between a supply voltage and an output node of the inverter. The second converter is coupled between the output node of the inverter and a ground voltage. The first converter, the second converter, or both include diode-connected transistors. The propagation delay time of the inverter is substantially a linear function of the temperature of the inverter.