Compensated Oscillator Circuit for Temperature-Stable Clock Frequency
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Solution Overview
Problem
Oscillator circuits experience frequency variations due to ambient temperature and process drift, affecting the stability of clock signals used in various electronic circuits.
Innovation Solution
The oscillator circuit incorporates a signal generator that produces a compensation frequency signal, converted into compensation binary pulses with constant pulse duration, which are used to adjust the duty cycle of charge currents to maintain constant charging rates of capacitors, thereby offsetting drift variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant current sources control capacitor charging to determine oscillator frequency, then the oscillator can generate stable clock signals, but ambient temperature variations and process drift cause frequency variations
Solution Approach 1:
The patent implements a feedback mechanism where the oscillator output signal is fed back to control the charge current to the capacitor. The output signal transitions cause the charge current to switch between first and second current sources, creating a feedback loop that automatically adjusts the charging process to maintain stable frequency despite temperature and process variations
Solution Approach 2:
The patent changes the current parameter dynamically by switching between multiple current sources (first and second current sources) based on the oscillator state. This parameter change approach allows the system to compensate for drift variations by adjusting the effective charge current to maintain constant frequency
2Reliability
If multiple current sources are used to compensate for drift variations, then frequency stability improves, but circuit complexity increases
Solution Approach 1:
The oscillator circuit components serve multiple functions: the same capacitor is used for both frequency determination and temperature compensation; the output signal simultaneously drives the load and provides feedback for current switching; the current sources serve both normal operation and drift compensation. This multi-functionality reduces the need for separate compensation circuits
Data Source
AI summary
An oscillator circuit includes a signal generator having a compensation frequency output node that provides a compensation frequency signal at the compensation frequency output node. A pulse generator having a pulsed signal output node and a pulse generator input node is coupled to the compensation frequency output node and converts the compensation frequency signal into a series of compensation binary pulses having a constant pulse duration regardless of variations in the duty cycle of the compensation binary pulses. An oscillator module having at least two capacitors, an oscillator output node and a pulsed signal input node is coupled to the pulsed signal output node, and provides an output signal that is at a frequency dependent on charging rates of the capacitors. Drift variations in the capacitors are offset by variations in a duty cycle of the compensation binary pulses supplied in order to maintain constant charging rates of the capacitors.