Locked Loop Frequency Correction Using an Untrimmed RC Oscillator
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Solution Overview
Problem
Existing locked loop circuits face challenges with process variations in RC oscillators, leading to inaccurate reference frequency generation, which requires large and power-consuming digital-to-analog converters for calibration, resulting in increased area and power consumption.
Innovation Solution
A locked loop circuit that uses a frequency counter to measure the reference signal and adjust a multiplier to achieve the desired output frequency without a digital-to-analog converter, utilizing an un-trimmed RC oscillator to reduce area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an RC oscillator without feedback mechanism is used to generate reference frequency, then area and power consumption are reduced, but manufacturing precision deteriorates due to process variations
Solution Approach 1:
The locked loop circuit automatically detects and corrects frequency deviations from the un-trimmed RC oscillator through its feedback mechanism, enabling the system to self-adjust without external calibration. This allows the use of simple, area-efficient un-trimmed oscillators while maintaining accurate output frequencies.
Solution Approach 2:
The locked loop circuit employs a feedback mechanism that continuously monitors the output frequency and adjusts the VCO accordingly. This feedback system compensates for process variations in the RC oscillator, maintaining frequency accuracy without requiring precision-trimmed components or large calibration DACs.
2Manufacturing precision
If a large DAC is used to achieve high accuracy in feedback signal generation, then manufacturing precision is improved, but area and power consumption increase
Solution Approach 1:
The system uses an un-trimmed RC oscillator that intentionally accepts some level of frequency inaccuracy, relying on the locked loop's frequency correction capability rather than attempting to achieve high precision through a large DAC. This partial action approach trades initial frequency accuracy for reduced hardware complexity.
Solution Approach 2:
The patent replaces expensive, large-area precision-trimmed oscillators and large calibration DACs with simpler, smaller components. The un-trimmed RC oscillator and minimal calibration mechanism serve as cost-effective substitutes that achieve sufficient accuracy through the locked loop's frequency synthesis capability.
3Manufacturing precision
If a crystal oscillator is used to generate reference frequency, then manufacturing precision is improved, but cost and area increase
Solution Approach 1:
The patent substitutes expensive crystal oscillators with inexpensive un-trimmed RC oscillators. The frequency accuracy previously provided by crystal oscillators is achieved instead through the locked loop circuit's frequency synthesis and correction mechanisms, significantly reducing cost and area.
Solution Approach 2:
The patent replaces the mechanical resonance-based crystal oscillator system with an electronic RC oscillator system controlled by a locked loop. This substitution uses electronic feedback and frequency synthesis to achieve the frequency stability and accuracy that previously required mechanical quartz crystal resonance.
Data Source
AI summary
An electronic device disclosed herein includes a locked loop circuit configured to receive a reference signal intended to have an intended frequency, wherein the locked look circuit is intended to generate an intended output signal having an intended frequency equal to the intended frequency multiplied by an intended multiplier. A frequency counter counts a number of pulses of the reference signal during a time window so as to determine an actual frequency of the reference signal. A control circuit determines an actual multiplier for the locked loop circuit that, when multiplied by the actual frequency of the reference signal, causes the locked loop circuit to generate an actual output signal having an actual frequency equal to the intended frequency.