Time Domain Temperature Sensor Clock Cycle Independence
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Solution Overview
Problem
The precision and consistency of time domain integrated temperature sensors are compromised due to variations in the cycle of the clock signal, particularly in applications like passive RFID tags, where different card readers produce inconsistent carrier frequencies, leading to varying temperature readings.
Innovation Solution
A time domain integrated temperature sensor design that includes a PTAT time delay circuit, a CTAT time delay circuit, an XOR gate, and a counter, with a pulse shaping circuit to shape the input clock signal into a square wave with a constant high voltage-level time, ensuring that the capacitors are charged uniformly, independent of the clock signal cycle, thus eliminating the dependency of the temperature reading on the clock signal frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a time domain integrated temperature sensor uses a clock signal for time domain sampling, then the temperature measurement can be converted into digital code, but the measurement precision deteriorates when the clock signal cycle varies due to different card readers or working conditions
Solution Approach 1:
The patent changes the measurement parameter from direct time-domain pulse width measurement (which depends on clock cycle) to frequency-domain measurement by counting clock cycles during a fixed temperature-proportional time period. This parameter transformation makes the measurement independent of clock cycle variations, resolving the contradiction between automation and measurement precision.
2Ease of manufacture
If the temperature sensor integrates signal processing functions on a semiconductor chip, then the device complexity is reduced and ease of manufacture is improved, but the reliability deteriorates when external clock signal frequency varies
Solution Approach 1:
Instead of measuring temperature by timing a fixed-frequency clock signal (which fails when clock frequency varies), the patent inverts the approach by counting the number of clock cycles that occur during a temperature-determined time interval. This inversion makes the measurement reliable even when clock frequency varies, while maintaining the benefits of integrated circuit fabrication.
3Use of energy by moving object
If passive RFID tags use extracted carrier signals as clock signals, then the use of energy is reduced and the device can operate passively, but the measurement precision deteriorates because different card readers produce different carrier frequencies
Solution Approach 1:
The patent makes the temperature measurement system universal by designing it to accept any clock signal frequency while maintaining accurate measurements. The counter-based approach that counts clock cycles during a temperature-proportional interval works correctly regardless of the specific carrier frequency extracted from different card readers, enabling the same passive RFID tag to function accurately with multiple different card readers.
Data Source
AI summary
A time domain integrated temperature sensor described by the present invention adopts a shaped clock signal to control the charging time of capacitors, so that the capacitors generate charging time delay signals related to the cycle of an input clock, and a pulse signal related to pulse width, temperature and the cycle of the input clock is generated through logical XOR (Exclusive OR) operation on a time delay signal generated when the capacitors are charged by one way of PTAT (Proportional To Absolute Temperature) current in an above control manner and a time delay signal generated when the capacitors are charged by one way of CTAT (Complementary To Absolute Temperature) current in the same manner; then, the same input clock signal is adopted for quantifying the pulse width of the pulse signal, the relevance of the obtained quantization result and the cycle of the input clock is completely offset, namely, an output value of the temperature sensor is unrelated to the input clock signal, thereby solving the problem that the reading of the existing time domain integrated temperature sensor is inconsistent as the cycle of the clock signal changes and improving the precision of the time domain integrated temperature sensor to a certain degree.