Oscillator Bias Current Compensation for Temperature-Stable Frequency
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Solution Overview
Problem
Electronic devices, particularly input devices with proximity sensors, face challenges in maintaining stable oscillation frequencies over a wide range of temperatures due to the temperature-dependent nature of oscillators.
Innovation Solution
An oscillator circuit design that includes multiple transistors, adjustment transistors, and auxiliary current sources to adjust and maintain the temperature coefficient, allowing the oscillation frequency to remain stable by placing transistors in weak inversion mode and using digital-to-analog converters to control current ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an oscillator is used to provide clock signals, then the oscillation frequency can be adjusted, but the frequency becomes unstable over wide temperature ranges
Solution Approach 1:
The patent applies parameter changes by adjusting the temperature coefficient of the oscillator circuit through controlled current injection. Auxiliary current sources modify the operating parameters of oscillator transistors to compensate for temperature-induced frequency drift, allowing the oscillator to maintain stable frequency across wide temperature ranges while preserving frequency adjustability through the switch-controlled current division.
Solution Approach 2:
The patent implements feedback mechanisms where auxiliary current sources continuously adjust the oscillator transistor operating points based on temperature compensation requirements. The circuit uses feedback loops that monitor frequency stability and automatically adjust bias currents to counteract temperature effects, ensuring reliable frequency stability while maintaining the ability to adjust oscillation frequency through the main current switch.
2Reliability
If auxiliary current sources are added to adjust temperature coefficient, then frequency stability improves, but circuit complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the current control function into distinct modules: main current sources for frequency setting, auxiliary current sources for temperature compensation, and a switch for current division. This modular segmentation allows each component to perform its specific function independently, making the complex circuit more manageable and maintainable while achieving both frequency stability and adjustability.
Solution Approach 2:
The patent implements multi-functionality where the auxiliary current sources serve dual purposes: they compensate for temperature effects on frequency stability while also allowing for programmable frequency adjustment when combined with the switch-controlled main current division. This universal approach enables a single circuit architecture to achieve both temperature compensation and frequency programmability without requiring separate dedicated circuits for each function.
Data Source
AI summary
An oscillator circuit is disclosed. The oscillator circuit includes: oscillator transistors including gates; adjustment transistors coupled to the gates; a differential output coupled to the oscillator transistors; a switch configured to set an oscillation frequency of the differential output by driving: a first current including a first portion of a main current through at least one of the oscillator transistors; and a second current including a second portion of the main current through at least one of the adjustment transistors; a first set of auxiliary current sources configured to adjust a temperature coefficient of the oscillator circuit by driving a first set of auxiliary currents through the oscillator transistors; and a second set of auxiliary current sources configured to maintain the oscillation frequency of the differential output by driving, in response to driving the first set of auxiliary currents, a second set of auxiliary currents though the adjustment transistors.