Ring Oscillator Bias Circuit for Temperature-Stable Frequency
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Solution Overview
Problem
Existing oscillators struggle to maintain a constant oscillation frequency under varying environmental conditions, particularly when power consumption is reduced, as the drain-source current of MOS transistors exhibits a positive temperature characteristic, leading to fluctuations in oscillation frequency.
Innovation Solution
The oscillator is configured with a current source and voltage source to provide a reference current and supply voltage with a negative temperature characteristic, using current mirrors and resistors to maintain a constant oscillation frequency by offsetting the increase in drain-source current due to temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power supply voltage is lowered to reduce power consumption, then power consumption is reduced, but the drain-source current exhibits a positive temperature characteristic causing oscillation frequency to vary
Solution Approach 1:
The patent changes the operating parameters of the MOS transistors by controlling the drain-source current to have a negative temperature characteristic. This is achieved through a compensation circuit that adjusts the current parameters to offset the positive temperature characteristic that would normally occur at low power supply voltages, thereby maintaining oscillation frequency stability while reducing power consumption.
Solution Approach 2:
The patent employs a feedback mechanism where the temperature characteristic of the drain-source current is monitored and compensated. The compensation circuit uses the temperature dependence of the current to generate a counteracting effect, creating a closed-loop system that maintains constant oscillation frequency despite temperature variations and low power supply voltage conditions.
2Reliability
If the drain-source current is increased to maintain oscillation frequency, then oscillation frequency stability is improved, but power consumption increases
Solution Approach 1:
Instead of increasing the overall power supply voltage to maintain frequency stability, the patent changes the temperature characteristic parameter of the drain-source current from positive to negative. This allows the system to maintain stable oscillation frequency through parameter optimization rather than brute-force power increase, thereby avoiding excessive power consumption.
3Reliability
If MOS transistors operate in the state with negative temperature characteristic, then oscillation frequency is stable, but power consumption is high
Solution Approach 1:
The patent creates a feedback loop where the temperature characteristic of the current is continuously compensated. The system detects the temperature-induced current variations and applies compensating adjustments, allowing the transistors to operate in a low-power state while maintaining the effective negative temperature characteristic needed for frequency stability through active control rather than passive high-power operation.
Data Source
AI summary
A low-power oscillator maintains its oscillation frequency regardless of environmental conditions. The oscillator includes a reference current source, a voltage source and a ring oscillator. The reference current source outputs a reference current depending on a first power supply voltage, and the voltage source outputs a second power supply voltage depending on the reference current. The oscillation frequency of the ring oscillator depends on the second power supply voltage.