Relaxation Oscillator Overshoot Integration for Stable Clock Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing relaxation oscillators lack accuracy and stability in generating high-frequency clock signals, particularly in comparison to crystal oscillators, and require complex calibration and high power consumption.
Innovation Solution
A sawtooth relaxation oscillator with overshoot error integration that charges an oscillation capacitor to a target voltage, then integrates and adjusts for overshoot errors, providing a stable clock frequency and fast startup with reduced power consumption and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a simple RC relaxation oscillator is used, then the device size and cost are reduced, but the clock frequency accuracy deteriorates
Solution Approach 1:
The patent implements feedback by integrating the overshoot error voltage back into the oscillation capacitor through a controlled current source. The error integrator continuously monitors the overshoot and adjusts the target voltage by applying a corrective current proportional to the integrated error, creating a closed-loop system that automatically compensates for frequency deviations without requiring external calibration components
Solution Approach 2:
The patent replaces the traditional mechanical trimming process (physical adjustment of resistor or capacitor values during assembly) with an electronic calibration sequence. A calibration module generates test oscillations at different frequencies, measures the actual frequency using a frequency-to-voltage converter, and uses a digital-to-analog converter to adjust the target voltage until the measured frequency matches the desired value, eliminating the need for physical trimming components
2Device complexity
If traditional relaxation oscillators are used, then the circuit is simple, but the frequency stability over temperature and time deteriorates
Solution Approach 1:
The error integrator continuously monitors the overshoot voltage that occurs when the oscillation capacitor charges beyond the target voltage. By integrating this error signal and feeding it back to adjust the target voltage, the system creates a self-correcting mechanism that compensates for drift caused by temperature variations and component aging, maintaining frequency stability without adding complex temperature sensing or compensation circuits
Solution Approach 2:
The oscillator performs its own calibration and compensation without external intervention. The calibration sequence automatically executes upon power-up, measuring the actual frequency and adjusting the target voltage through digital-to-analog conversion. During operation, the error integrator continuously self-corrects frequency deviations by integrating overshoot errors and adjusting the target voltage in real-time, making the system self-regulating
3Speed
If fast startup is implemented, then the oscillator reaches frequency quickly, but overshoot increases
Solution Approach 1:
The patent converts the harmful overshoot effect into a useful signal by capturing the overshoot voltage when the oscillation capacitor exceeds the target voltage and using it as the input to the error integrator. This overshoot voltage, instead of being discarded as a disturbance, becomes the basis for generating the corrective current that adjusts the target voltage, transforming the startup problem into the mechanism for frequency calibration and compensation
Solution Approach 2:
The patent implements periodic calibration sequences that execute at regular intervals, including upon power-up and at predetermined times during operation. Each calibration cycle temporarily modifies the oscillation waveform by charging the capacitor to a higher voltage, measuring the resulting frequency, and adjusting the target voltage. This periodic action allows the system to maintain accuracy over time while the error integration continuously operates between calibration cycles
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 improves clock frequency accuracy by an order of magnitude, offers stable frequency over temperature and time, and enables convenient initial calibration, while reducing power consumption and noise.
Implementation Method 1
A smaller and less expensive RC relaxation oscillator can use a resistor and a capacitor to achieve a time constant to establish the clock frequency
Implementation Method 2
interrupt charging before beginning an error integration phase that adjusts the target voltage by integrating an overshoot error of a voltage on the oscillation capacitor
Data Source
AI summary
A relaxation oscillator can provide a smaller and cheaper alternative to a crystal oscillator circuit in a wide variety of applications. A sawtooth relaxation oscillator can include overshoot error integration. Separate and distinct oscillator capacitor charging, overshoot error integration, and reset phases can be provided using separate comparators for first and second oscillation capacitors. Potential advantages can include high accuracy high-frequency clock, convenient trimming during initial calibration, clock frequency stability over temperature and time, fast startup with low overshoot, high power supply rejection, low power, or low noise/jitter. The oscillator can charge an oscillation capacitor up to a target voltage, then interrupt charging before beginning an error integration phase that adjusts the target voltage by integrating an overshoot error of a voltage on the oscillation capacitor. After completing the overshoot error integration, the voltage on the oscillation capacitor can be reset. The techniques described are believed to be capable of improving clock frequency accuracy and other characteristics.