Closed-Loop Ring Oscillator Frequency Control Without External Reference
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Solution Overview
Problem
Ring oscillators in electronic systems experience significant frequency variations due to manufacturing process, supply voltage, and temperature fluctuations, leading to unstable clock signal outputs, which existing technologies fail to adequately mitigate without relying on external reference supplies, resulting in high power consumption.
Innovation Solution
A closed-loop feedback control system is implemented, using a regulator and oscillator coupled with a resistor and a feedback controller, which applies a control voltage to adjust the oscillator frequency by trimming variable transistors and resistors, maintaining frequency stability independently of process variations and temperature changes without external references.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external reference supplies are used to stabilize oscillator frequency, then frequency stability is improved, but power consumption increases
Solution Approach 1:
The oscillator circuit uses its own output signal to generate the reference voltage through a feedback path containing a resistor and differential amplifier, eliminating the need for external reference supplies. The circuit serves itself by recycling its output back to control its own frequency, thereby reducing power consumption while maintaining stability.
Solution Approach 2:
A feedback loop is implemented where the oscillator output is fed back through a resistor to a differential amplifier that compares it with a portion of the oscillator signal, generating a control voltage that adjusts the oscillator frequency. This closed-loop feedback mechanism stabilizes frequency without requiring external references.
2Device complexity
If manufacturing process variations are not compensated, then device complexity is reduced, but frequency stability deteriorates
Solution Approach 1:
The feedback loop continuously monitors the oscillator output and adjusts the frequency by applying a control voltage through the differential amplifier. This automatic adjustment compensates for manufacturing variations without requiring complex calibration circuits or external references, achieving stability through a relatively simple feedback structure.
Solution Approach 2:
The circuit automatically compensates for its own manufacturing variations by using its output to generate the control signal. The oscillator self-adjusts its frequency by recycling its output through the feedback path, eliminating the need for external compensation mechanisms.
3Reliability
If temperature compensation mechanisms are added, then frequency stability is improved, but device complexity increases
Solution Approach 1:
The feedback loop inherently compensates for temperature effects by continuously adjusting the oscillator frequency based on its actual output. As temperature changes affect the oscillator, the feedback mechanism detects the frequency deviation and applies corrective control voltage, achieving temperature compensation without separate compensation circuits.
Solution Approach 2:
The oscillator circuit self-compensates for temperature variations by using its own output signal to generate the control voltage that adjusts its frequency. The circuit adapts to temperature changes automatically without requiring external temperature sensors or compensation networks.
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 solution achieves stable oscillator output frequencies with reduced power consumption, minimizing the impact of manufacturing process and temperature fluctuations, and allows for fine and coarse adjustments to maintain PLL lock, thereby enhancing the reliability and efficiency of electronic systems.
Implementation Method 1
a feedback controller that includes a differential amplifier coupled between the oscillator, the resistor and the regulator, wherein the feedback controller is configured to apply a control voltage to the regulator in response to a resistor voltage upon the resistor and an oscillator voltage upon the oscillator
Data Source
AI summary
An electronic device comprises a regulator, and an oscillator and a resistor coupled to the regulator. The electronic device further comprises a feedback controller that includes a differential amplifier coupled between the oscillator, the resistor, and the regulator. The feedback controller is configured to apply a control voltage to the regulator in response to a resistor voltage upon the resistor and an oscillator voltage upon the oscillator. The feedback controller can be coupled to control a substantially equal voltage upon the resistor and the oscillator.