Integrated Circuit Temperature Measurement Using Switched Capacitor
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Solution Overview
Problem
Existing electronic components, such as crystal oscillators in wireless communication systems, face performance variations due to temperature changes, which limits their operating temperature range and requires expensive temperature-compensated solutions or complex calibration methods.
Innovation Solution
An integrated circuit with a switched capacitor and a thermistor, coupled with an analog-to-digital converter and controller, measures temperature and adjusts the equivalent resistance of the switched capacitor to compensate for temperature variations, allowing for accurate temperature measurement and frequency stabilization without the need for multiple calibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a standard crystal oscillator is used to generate reference clock signals, then the cost is reduced, but the operating temperature range is limited due to frequency drift with temperature
Solution Approach 1:
The patent replaces mechanical/physical temperature compensation mechanisms (like those in TCXOs) with an electronic measurement and compensation system. A thermistor senses temperature, an ADC converts the resistance measurement to digital form, and a controller calculates compensation values to adjust the oscillator frequency, thereby extending the operating temperature range without using expensive temperature-compensated crystal oscillators
Solution Approach 2:
The patent introduces a thermistor as an intermediary sensing element that indirectly measures the temperature of the crystal oscillator. This thermistor couples to the oscillator package and provides temperature information to the measurement circuit, enabling compensation without direct contact with the oscillator itself
2Measurement precision
If multiple resistors are switched to measure temperature, then temperature measurement is achieved, but the system complexity and calibration requirements increase
Solution Approach 1:
The patent extracts the temperature sensing function from complex multi-resistor switching networks and implements it using a single external thermistor coupled with a simple switched-capacitor measurement circuit integrated on the chip. This reduces the number of components and simplifies the overall system while maintaining temperature measurement capability
Solution Approach 2:
The measurement circuit uses the chip's existing resources (switched capacitors, ADC, controller) to perform temperature measurement without requiring external complex measurement infrastructure. The switched capacitor leverages the chip's own switching infrastructure to create a variable resistance that interfaces with the thermistor
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 provides accurate temperature measurement and compensation for frequency drift, enabling a wider operating temperature range without the expense of temperature-compensated crystal oscillators, while maintaining measurement accuracy across a broad temperature range.
Implementation Method 1
a thermistor external to the integrated circuit is to couple to the divider node
Implementation Method 2
a switched capacitor coupled between a supply voltage node and a divider node
Data Source
AI summary
In an embodiment, an integrated circuit includes: a switched capacitor coupled between a supply voltage node and a divider node, where a thermistor external to the integrated circuit is to couple to the divider node; an analog-to-digital converter (ADC) coupled to the divider node to receive a voltage at the divider node and generate a digital value based thereon; and a controller coupled to the ADC to determine a temperature associated with the thermistor based at least in part on the digital value.