Trim-Capable Oscillator Circuit for Stable Frequency With Polysilicon
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Internal oscillators, particularly those using polysilicon components, suffer from imprecision due to high temperature coefficients, leading to variability in output signals, which is costly to mitigate with precise components like silicide poly-resistors or ZTCR components.
Innovation Solution
Implementing a trim-capable current source with trimmable resistors and capacitors within the oscillator, allowing for resistance and capacitance trimming to adjust charging currents and charge times, thereby compensating for process and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polysilicon components are used in internal oscillators, then fabrication cost is reduced, but temperature coefficient increases leading to frequency instability
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the oscillation frequency based on temperature measurements. A temperature sensor monitors the oscillator temperature, and a control circuit modifies the frequency parameter to compensate for thermal drift caused by polysilicon components' high temperature coefficients, thereby maintaining frequency stability without requiring expensive low-TCR materials
Solution Approach 2:
The patent implements feedback control by continuously monitoring the oscillator's output frequency and comparing it to a reference frequency. When deviations are detected, the system adjusts the frequency control voltage to correct the deviation, creating a closed-loop system that compensates for temperature-induced frequency variations in polysilicon-based components
2Manufacturing precision
If silicide poly-resistor or ZTCR components are used, then temperature coefficient is reduced improving precision, but fabrication cost increases
Solution Approach 1:
The patent uses inexpensive polysilicon components instead of expensive silicide or ZTCR components, accepting that these cheaper components have higher temperature coefficients. The cost savings from using disposable-like inexpensive components are offset by implementing low-cost digital compensation algorithms and trim circuits that correct for the temperature drift, achieving precision without high material costs
Solution Approach 2:
The patent substitutes physical/material solutions (using expensive low-TCR materials) with a digital/electronic solution (temperature sensing and digital frequency adjustment). Instead of relying on the inherent physical properties of expensive materials to provide temperature stability, the system uses electronic feedback and digital processing to achieve the same stability goal more cost-effectively
Data Source
AI summary
Trimming components within an oscillator comprising: a trim-capable current source, wherein the trim-capable current source comprises a trimmable resistor and a trimmable current component, a comparator comprising a first input terminal that couples to the trim-capable current source and the second input terminal that couples to a reference voltage source, a switch coupled to the first input terminal and the trim-capable current source, and a trim-capable capacitor coupled to the switch, wherein the switch is coupled between the trim-capable capacitor and the trim-capable current source.