LC Frequency Reference Generator With Temperature-Based Frequency Correction
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Solution Overview
Problem
Existing integrated frequency reference generators face challenges in achieving ±100 ppm absolute frequency accuracy over temperature and lifetime due to process spread and temperature dependency, requiring costly multi-temperature trimming or re-trimming, while traditional quartz crystal oscillators are bulky and expensive.
Innovation Solution
A frequency reference generator with a temperature sensor generating a DC voltage based on operating temperature, used to improve frequency stability and control frequency-adjustment circuitry, employing a Colpitts oscillator and frequency divider with sample-specific and sample-agnostic mappings to minimize process, voltage, and temperature variations, allowing for 1T-trim and field compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quartz crystal oscillators are used to achieve ppm-level frequency accuracy, then frequency accuracy is improved, but device size and cost increase
Solution Approach 1:
The patent extracts the frequency reference generation function from traditional quartz crystal oscillators and implements it using an integrated LC oscillator circuit on a semiconductor chip. This removes the bulky crystal oscillator component while maintaining frequency reference functionality through an entirely different technological approach using on-chip inductors and capacitors.
Solution Approach 2:
The patent replaces the mechanical quartz crystal oscillator system with an electronic LC oscillator system. The mechanical resonance of quartz crystals is substituted with electronic resonance using inductors and capacitors, enabling integration on semiconductor chips while achieving comparable frequency accuracy through electronic rather than mechanical means.
2Volume of moving object
If integrated frequency reference generators are used to reduce size, then device size is reduced, but frequency accuracy deteriorates due to process spread and temperature dependency
Solution Approach 1:
The patent implements a feedback mechanism using a temperature sensor that continuously monitors the operating temperature and feeds this information to a frequency adjustment circuit. This circuit dynamically adjusts the oscillation frequency of the LC oscillator to compensate for temperature-induced frequency drift, thereby maintaining frequency accuracy despite the integrated architecture's susceptibility to process and temperature variations.
Solution Approach 2:
The patent changes the operating parameters of the LC oscillator based on temperature conditions. By adjusting the oscillation frequency parameter in response to temperature sensor input, the system compensates for the inherent parameter drift caused by process spread and temperature dependency in integrated components, maintaining stable frequency output.
3Device complexity
If simple 1T-trim is used to reduce complexity, then device complexity is reduced, but frequency accuracy over temperature and lifetime is insufficient
Solution Approach 1:
The patent uses temperature sensor feedback to enable dynamic frequency compensation that operates continuously during device operation. This feedback-based approach replaces complex multi-temperature trimming procedures with a simpler one-time factory trim combined with automatic temperature-compensated adjustment during operation, reducing overall complexity while improving frequency stability across temperature and lifetime.
Solution Approach 2:
The patent implements a self-service mechanism where the frequency reference generator automatically compensates for its own temperature-induced frequency drift. The temperature sensor and frequency adjustment circuitry work together to self-correct frequency deviations without requiring external intervention or complex trimming procedures, thereby simplifying the system while maintaining high reliability.
4Measurement precision
If multi-temperature trim is used to achieve required accuracy, then frequency accuracy is improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent performs frequency trimming once during factory manufacturing at a single temperature condition. This preliminary one-time trim establishes the base frequency, and subsequent temperature-induced frequency variations are automatically compensated during operation by the temperature sensor and adjustment circuit. This eliminates the need for costly multi-temperature trimming processes while maintaining frequency accuracy.
Solution Approach 2:
The patent uses real-time temperature feedback to compensate for frequency drift that would otherwise require multiple trimming steps. By continuously monitoring temperature and adjusting frequency accordingly, the system achieves the frequency stability that would normally require complex multi-temperature factory trimming, thereby significantly reducing manufacturing cost and process complexity.
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
The solution achieves ±120 ppm frequency accuracy from -50°C to 170°C with minimal temperature coefficient of frequency, reducing frequency drift and process spread, and maintains stability over lifetime with reduced trimming needs.
Implementation Method 1
a temperature sensor that generates a DC voltage whose voltage level is dependent on an operating temperature of the frequency reference generator
Implementation Method 2
an integrated frequency source that includes a resonant tank and drive circuitry that drives the resonant tank to generate an oscillator signal
Data Source
AI summary
A frequency reference generator includes (i) an integrated frequency source having drive circuitry that drives a resonant (e.g., non-trimmable LC) tank to generate an oscillator signal, (ii) at least one temperature sensor that generates at least one measured temperature signal, and (iii) a frequency-adjustment circuit that adjusts the oscillator signal frequency to generate the frequency reference based on the measured temperature signal and a (e.g., sample-specific) mapping from temperature to a corresponding frequency-adjustment parameter (e.g., a divisor value for a fractional frequency divider). In some embodiments, a Colpitts oscillator generates the oscillator signal based on the measured temperature signal, where the Colpitts oscillator has voltage/temperature-compensation circuitry that compensates for variations in power supply voltage and operating temperature. Such frequency reference generators achieve substantial PVT insensitivity with as little as a single 1T-trim or even no trim at all.