One-Point Calibration Temperature Sensor for Wireless RFID
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Solution Overview
Problem
Existing temperature sensors for microelectronic applications require multiple calibration points due to nonlinear temperature dependence, leading to increased power consumption, additional circuitry, and costs, which is undesirable in low-power wireless RFID tags.
Innovation Solution
A low-power, one-point calibration analog linear temperature sensor is integrated into wireless transceiver platforms, utilizing a single calibration point to establish a linear relationship between temperature and differential voltages, minimizing power consumption and chip area, and fabricated using generic CMOS technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PTAT or CTAT circuits are used for temperature sensing, then temperature measurement capability is provided, but multiple calibration points are required due to nonlinear temperature dependence
Solution Approach 1:
The patent changes the fundamental parameter relationship by using a sensor whose output is inherently linear with temperature, eliminating the need for nonlinear correction. The sensor design ensures that the differential voltage between two diodes changes linearly with temperature, allowing single-point calibration to establish the scaling factor directly.
Solution Approach 2:
The patent extracts only the essential calibration information (single scaling factor) needed for accurate temperature measurement, removing the complexity of multiple calibration points and lookup tables. This is achieved by designing the sensor to produce a linear response that requires minimal calibration data.
2Measurement precision
If multiple calibration points and lookup tables are used, then temperature measurement accuracy is improved, but power consumption and memory requirements increase
Solution Approach 1:
The patent changes the output characteristic of the temperature sensor to be linear with temperature, which eliminates the need for power-consuming lookup tables and complex calibration procedures. The linear relationship allows direct calculation of temperature from a single calibration point, significantly reducing power consumption in wireless RFID tags.
3Measurement precision
If additional circuitry is added to nullify nonlinearities, then temperature measurement accuracy is improved, but chip area and power consumption increase
Solution Approach 1:
The patent fundamentally changes the sensor design to produce a linear temperature response from the outset, eliminating the need for additional circuitry to correct nonlinearities. This is achieved by using two diodes with different current densities and taking the difference of their forward voltages, which creates a linear relationship with temperature.
4Measurement precision
If external temperature sensors are used, then temperature sensing capability is provided, but additional bonding pads, mounting, and calibration costs increase
Solution Approach 1:
The patent merges the temperature sensing function with the existing RFID tag circuitry by integrating diodes and associated circuitry directly into the chip. This eliminates the need for separate external temperature sensors, bonding pads, and mounting procedures, reducing manufacturing complexity and cost.
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 solution enables low-cost, low-power temperature sensing over industrial and medical ranges with minimal power consumption, reducing calibration complexity and costs, while maintaining high accuracy and precision for various sensing applications.
Implementation Method 1
a linear relationship between actual temperature and measured differential voltages (currents) is theoretically predicted by the very nature of the device physics of the temperature sensing elements themselves
Data Source
AI summary
A low power analog linear temperature sensor integrateable with digital and/or analog circuits in CMOS fabrication processes. The sensor is accurately calibrateable at a single temperature that yields a linear relationship between measured differential voltage and temperature over a wide variety of temperature ranges. The sensor provides stable voltage and current references that are essential for wireless sensor platforms. There are many applications where sensors require stable voltage/current references and the physics of the sensor's transduction mechanisms are themselves temperature dependent. Wireless platforms such as, but not limited to, passive RFID tags with the addition of on- or off-chip sensors provide a low cost solution for a variety of low cost sensor applications.