RC Oscillator Temperature Compensation for Stable Sleep Timing
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Solution Overview
Problem
RC oscillators in low power consumption applications, such as IoT and BLE, face challenges in maintaining frequency accuracy and stability due to temperature variations, which affect the system's sleep timing and power consumption.
Innovation Solution
The RC oscillator design incorporates an input module for two-path charging currents and a bias current, an oscillating module with a Sigma-Delta modulator for frequency tuning, an inverting module with a Schmitt trigger, and compensating modules to adjust for temperature-induced frequency deviations, including a second current source with a negative temperature coefficient to stabilize the oscillation frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a basic RC relaxation oscillator is used, then the circuit is simple and low power consumption is achieved, but frequency accuracy and stability deteriorate due to temperature variations
Solution Approach 1:
The oscillator is divided into multiple independent modules: oscillating module, inverting module, first compensating module, second compensating module, and output module. Each module performs a specific function, allowing frequency accuracy improvement through dedicated compensating modules without significantly increasing overall power consumption.
Solution Approach 2:
The patent changes the temperature coefficient parameter of the resistor from conventional positive values to negative temperature coefficient values. This parameter change enables the resistor to compensate for temperature-induced frequency drift, improving frequency accuracy while maintaining low power consumption characteristics.
2Reliability
If temperature compensation is implemented using conventional methods, then frequency stability improves, but device complexity increases
Solution Approach 1:
The compensating modules are merged with the basic RC oscillator structure rather than being separate external components. The first and second compensating modules integrate temperature compensation functions directly into the oscillator circuit, improving frequency stability without adding significant external complexity.
Solution Approach 2:
The compensating modules serve multiple functions: they compensate for temperature variations, adjust frequency accuracy, and maintain oscillation stability simultaneously. This multi-functionality reduces the need for additional separate components, thereby limiting complexity increase.
3Measurement precision
If high precision frequency tuning is implemented, then frequency accuracy improves, but power consumption increases
Solution Approach 1:
The oscillator implements dynamic frequency tuning through the inverting module and compensating modules that actively adjust operating parameters based on temperature and frequency deviation. This dynamic adjustment achieves high frequency tuning accuracy without requiring continuously high power consumption, as adjustments are made only when needed.
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 design improves the frequency tuning accuracy and stability of the RC oscillator, reducing the correlation between oscillating frequency and temperature, thereby enhancing the precision of sleep timing and reducing power consumption in low power consumption applications.
Implementation Method 1
A capacitor is charged with a fixed current, and a voltage across the capacitor is compared with a reference voltage by a comparator
Implementation Method 2
using a resistor with an ultra-low temperature coefficient in special processes; using an off-chip resistor with a low temperature coefficient; a second current source with a negative temperature coefficient to stabilize the oscillation frequency
Data Source
AI summary
An RC oscillator is provided for improving stability of oscillation frequency. The circuit includes an input module, an oscillating module, an inverting module, first and second compensating modules and an output module, wherein the input module provides two-path charging currents and bias current for the oscillating module; the oscillating module outputs a first high level or a first low level to the inverting module under the control of the two-path charging currents and bias current, and improves frequency tuning accuracy of the oscillator; the inverting module inverts the first high level to a second low level or inverts the first low level to a second high level, and outputs the second low level or the second high level to the output module; the output module outputs the second high level and the second low level; and the first and second compensating modules improve stability of the oscillation frequency.