Frequency-Locked Loop Resistance Drift Correction for Temperature Stability
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Solution Overview
Problem
Existing frequency-locked loops (FLLs) face challenges in correcting oscillation frequency due to temperature variation without increasing circuit area and complexity, as current methods often require additional phase-locked loops (PLLs) to detect frequency drifting.
Innovation Solution
A frequency-locked loop (FLL) that monitors resistance drifting of at least two resistors due to temperature variation, correcting the oscillation frequency by adjusting the resistance based on detected differences, without significantly increasing overall costs or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional phase-locked loops (PLLs) are used to detect frequency drifting, then frequency correction capability is improved, but circuit area and complexity increase significantly
Solution Approach 1:
The patent extracts only the essential frequency detection function from a full PLL circuit, implementing a simplified frequency detector that monitors oscillation frequency without requiring the complete PLL architecture. This selective extraction maintains frequency correction capability while dramatically reducing circuit complexity and area.
Solution Approach 2:
The patent creates a simplified copy of the PLL's frequency detection functionality rather than implementing a full additional PLL. The frequency detector replicates only the necessary measurement capability, avoiding the overhead of complete phase-locked loop implementations and thereby reducing overall circuit complexity.
2Manufacturing precision
If loading capacitors are adjusted to correct process corner variation, then oscillation frequency accuracy is improved, but the system remains sensitive to temperature variation
Solution Approach 1:
The patent implements a feedback mechanism where the frequency detector continuously monitors the oscillation frequency and provides correction signals to the variable delay elements. This closed-loop feedback enables real-time compensation for temperature-induced frequency drift, allowing the system to maintain accuracy across varying thermal conditions.
Solution Approach 2:
The patent transforms the static capacitor adjustment approach into a dynamic system with variable delay elements that can be continuously adjusted in response to temperature changes. This dynamic adaptation allows the oscillator to maintain precise frequency operation across different temperature conditions, overcoming the limitation of fixed capacitor-based correction.
3Area of stationary object
If a novel architecture is designed to correct frequency drift without additional PLLs, then circuit area is reduced, but implementation complexity may increase
Solution Approach 1:
The patent segments the frequency correction function into distinct modular components: a frequency detector, a correction logic unit, and variable delay elements integrated within the ring oscillator stages. This segmentation allows each component to be optimized independently and simplifies the overall implementation by distributing functionality across manageable modules rather than requiring a monolithic complex architecture.
Solution Approach 2:
The patent merges the frequency detection and correction functions directly into the existing oscillator structure, integrating the frequency detector and correction logic with the ring oscillator stages. This consolidation eliminates the need for separate additional PLL circuits, reducing overall circuit area while managing complexity through functional integration rather than addition.
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
Effectively corrects oscillation frequency drifts caused by temperature variation, maintaining stability without introducing side effects or significantly increasing circuit size.
Implementation Method 1
For a free run ring oscillator, an oscillation frequency thereof is determined by delays of circuit stages of the ring oscillator
Implementation Method 2
the resistance of at least one of the two resistors is one of factors that determines the oscillation frequency, and is also a main factor which cause the frequency drifting due to temperature variation
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A frequency-locked loop (FLL) and a method for correcting an oscillation frequency of an output signal of the FLL are provided. The FLL includes a switched capacitor circuit, a first resistor set, a second resistor set, a determination circuit and a control circuit. The switched capacitor circuit includes a capacitor, and connection of the capacitor is switched according to the oscillation frequency. The first resistor set is configured to provide a first resistance, and the second resistor set is configured to provide a second resistance. The determination circuit is configured to generate a determination result according to the first resistance and the second resistance. The control circuit is configured to generate a control signal for correcting the first resistance and the second resistance according to the determination result, where the oscillation frequency is determined based on the capacitor and at least one of the first resistance and the second resistance.