Ring Oscillator RTC Calibration for Low-Power Time Accuracy
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Solution Overview
Problem
Microcomputers in IoT systems require a real-time clock that is low power consumption, small, and inexpensive while maintaining accuracy, which is challenging due to the high cost, size, and power consumption of quartz oscillators, and the difficulty in maintaining accuracy without them.
Innovation Solution
A real-time clock generation device using a first ring oscillator with a control-value table and a second ring oscillator for calibration, along with a divider and frequency measurer to adjust division ratios and maintain accuracy, while using low power and being cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a crystal oscillator is used as a reference clock, then the accuracy of the real-time clock is improved, but the cost, size, and power consumption increase
Solution Approach 1:
The patent changes the operating parameters of the ring oscillator by adjusting division ratios based on temperature zones and time zones. This allows the system to compensate for frequency drift and maintain accurate timekeeping without requiring a high-precision crystal oscillator, thereby reducing power consumption while preserving timing accuracy.
Solution Approach 2:
The patent replaces the mechanical quartz crystal oscillator with an electronic ring oscillator. This substitution eliminates the need for physical crystal resonance, enabling a compact, low-power implementation that achieves comparable timing accuracy through digital compensation methods rather than mechanical precision.
2Measurement precision
If a crystal oscillator is used as a reference clock, then the accuracy of the real-time clock is improved, but the device size increases
Solution Approach 1:
The patent replaces the mechanical quartz crystal oscillator with an electronic ring oscillator. This substitution eliminates the need for physical crystal resonance, enabling a compact, low-power implementation that achieves comparable timing accuracy through digital compensation methods rather than mechanical precision.
Solution Approach 2:
The patent changes the operating parameters of the ring oscillator by adjusting division ratios based on temperature zones and time zones. This allows the system to compensate for frequency drift and maintain accurate timekeeping without requiring a high-precision crystal oscillator, thereby reducing power consumption while preserving timing accuracy.
3Measurement precision
If a crystal oscillator is used as a reference clock, then the accuracy of the real-time clock is improved, but the cost increases
Solution Approach 1:
The patent replaces the mechanical quartz crystal oscillator with an electronic ring oscillator. This substitution eliminates the need for physical crystal resonance, enabling a compact, low-power implementation that achieves comparable timing accuracy through digital compensation methods rather than mechanical precision.
Solution Approach 2:
The patent changes the operating parameters of the ring oscillator by adjusting division ratios based on temperature zones and time zones. This allows the system to compensate for frequency drift and maintain accurate timekeeping without requiring a high-precision crystal oscillator, thereby reducing power consumption while preserving timing accuracy.
4Use of energy by moving object
If a ring oscillator is used instead of a crystal oscillator, then the power consumption, size, and cost are reduced, but the accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the ring oscillator's output frequency is continuously monitored and compensated by adjusting division ratios based on temperature and time zone data. This feedback loop corrects frequency drift, maintaining accurate timekeeping despite the inherent lower precision of ring oscillators compared to crystal oscillators.
Solution Approach 2:
The patent changes the operating parameters of the ring oscillator by adjusting division ratios based on temperature zones and time zones. This allows the system to compensate for frequency drift and maintain accurate timekeeping without requiring a high-precision crystal oscillator, thereby reducing power consumption while preserving timing accuracy.
Data Source
AI summary
A first ring oscillator outputs a reference clock signal. A table acquirer acquires a control-value table representing a correspondence between time zones in which the first ring oscillator operates and division ratios of the reference clock signal. In accordance with the control-value table, a divider generates an RTC signal by changing a division ratio of the reference clock signal for each time zone in which the first ring oscillator operates. During execution of calibration of the control-value table, a second ring oscillator outputs a measurement clock signal that oscillates more accurately than the reference clock signal. A frequency measurer measures a frequency of the RTC signal based on the measurement clock signal. In a case in which a frequency of the RTC signal exceeds an allowable error, an update determiner updates at least part of division ratios in the control-value table.