Temperature Stable Oscillator Circuit with Self-Heating Calibration
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Solution Overview
Problem
Microelectromechanical devices (MEMS) require temperature-stable oscillators without crystal bases, but existing non-crystal based oscillators face challenges in maintaining stable frequency output over temperature variations, and their testing and tuning processes are time-consuming and costly.
Innovation Solution
An oscillator circuit that includes current generators for absolute and proportional temperature currents, a temperature slope control circuit to adjust these currents, and a current-controlled oscillator, along with a self-heating mechanism and built-in self-test circuit for automated tuning, enabling temperature-independent frequency generation and efficient calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a quartz crystal is used to provide stable frequency output over temperature, then frequency stability is improved, but device area increases making it incompatible with MEMS space constraints
Solution Approach 1:
The patent replaces the mechanical quartz crystal oscillator with an electronic RC-based oscillator circuit that generates clock signals through resistive and capacitive elements integrated on-chip, eliminating the need for discrete crystal components while maintaining frequency generation functionality
Solution Approach 2:
The patent employs temperature compensation techniques by dynamically adjusting circuit parameters (resistor values, capacitor values, or transistor bias conditions) as a function of temperature to counteract thermal drift effects and maintain stable frequency output across temperature variations
2Reliability
If resistor trimming circuits are used to maintain constant resistance over temperature, then frequency stability is improved, but testing complexity and cost increase due to thermal cycling requirements
Solution Approach 1:
The patent implements self-heating elements within the oscillator circuit that generate controlled temperature increases during operation, enabling the circuit to self-test and self-calibrate its temperature compensation characteristics without requiring external thermal cycling equipment or complex test infrastructure
Solution Approach 2:
The patent incorporates feedback mechanisms where the oscillator monitors its own output frequency and temperature conditions, automatically adjusting trimming circuit parameters to maintain optimal performance across temperature ranges, thereby eliminating the need for manual testing and adjustment
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
The solution provides stable frequency output over a range of temperatures with improved frequency stability and reduced testing costs, allowing for quicker and more efficient calibration within MEMS devices.
Implementation Method 1
A self-heating apparatus may be included to vary temperature of the oscillator components in order to facilitate calibration of the oscillator.
Data Source
AI summary
An oscillator circuit includes a first current generator circuit that generates a current complementary to absolute temperature and a second current generator that generates a current proportional to absolute temperature. A temperature slope control circuit adjusts slopes of the current complementary to absolute temperature and the current proportional to absolute temperature in a complementary fashion and adds the current complementary to absolute temperature to the current proportional to absolute temperature after slope control to produce a temperature independent current. A current control circuit adjusts magnitude of the temperature independent current to produce a magnitude adjusted temperature independent current. A current controlled oscillator generates an output signal as a function of the magnitude adjusted temperature independent current.