Self-Calibrating RC Oscillator Without Charge Pump Drift
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Solution Overview
Problem
Conventional RC oscillators face limitations in generating high-accuracy frequencies due to voltage and temperature dependencies, requiring continuous power consumption for self-calibration using a charge pump.
Innovation Solution
A self-calibrating oscillator design that includes an oscillation circuit, pulse counter, charging circuit, reset circuit, and calibration circuit, which calibrates frequency by charging a capacitor and comparing its voltage with reference voltages, eliminating the need for a charge pump and optimizing power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a charge pump is used for self-calibration, then frequency accuracy is improved, but power consumption increases and device complexity increases
Solution Approach 1:
The patent removes the charge pump component from the self-calibration system. Instead of using a charge pump to generate calibration voltages, the invention uses a simple capacitor that charges through a resistor from the existing power supply, eliminating the need for complex voltage generation circuitry and reducing power consumption.
Solution Approach 2:
The calibration capacitor charges itself automatically through the resistor from the power supply voltage during normal operation. The system uses its own operating voltages and currents to perform calibration without requiring external calibration equipment or additional active components, enabling autonomous self-calibration with minimal power overhead.
2Measurement precision
If continuous self-calibration is performed, then frequency accuracy is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic self-calibration by monitoring the voltage across the calibration capacitor at specific intervals during normal oscillator operation. Rather than continuous calibration, the system periodically samples the capacitor voltage and adjusts calibration parameters, significantly reducing power consumption while maintaining frequency accuracy.
3Device complexity
If RC circuit is used for frequency generation, then device complexity is reduced, but frequency accuracy deteriorates due to voltage and temperature dependencies
Solution Approach 1:
The patent implements a feedback mechanism where the voltage across the calibration capacitor is continuously monitored and compared against expected values. Based on this feedback, the system automatically adjusts calibration parameters to compensate for voltage and temperature drift, maintaining frequency accuracy while keeping the RC oscillator structure simple.
Solution Approach 2:
The system dynamically adjusts calibration parameters based on operating conditions. By monitoring the capacitor voltage and comparing it with reference values, the system changes calibration parameters to compensate for environmental variations, allowing the simple RC circuit to maintain high frequency accuracy across different voltage and temperature conditions.
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 efficiently increases frequency accuracy by calibrating the oscillator without a charge pump, reducing power consumption and improving frequency stability across varying conditions.
Implementation Method 1
a capacitor C1, across which a voltage V1 is generated
Data Source
AI summary
A self-calibrating oscillator that increases the output frequency accuracy without using a charge pump includes an oscillation circuit, a pulse counter, a charging circuit, a reset circuit, a calibration circuit, and a timing control unit. The pulse counter counts a pulse signal having frequency f0 from the oscillation circuit based on a count start signal provided from the timing control unit, while providing an output signal to the charging circuit. The charging circuit connects a constant current source and capacitor when provided with the output signal to raise the voltage at the connection node. The calibration circuit provides the oscillation circuit with a calibration value for increasing the frequency if the voltage when the output of the output signal ends is higher than a high potential reference voltage and provides a calibration value for lowering the frequency if this voltage is lower than a low potential reference voltage.