Mixed-Filter PLL Circuit for PVT-Stable Frequency Control
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Solution Overview
Problem
As semiconductor integration advances, all-digital phase locked loop (PLL) circuits face challenges in precise control due to sensitivity to process, voltage, and temperature (PVT) variations, making it difficult to maintain stable frequency and phase synchronization in small semiconductor chips.
Innovation Solution
A phase locked loop circuit is designed with a bang-bang phase frequency detector, an analog-digital mixed filter, a voltage controlled oscillator, and a divider, incorporating a digital filter, delta-sigma modulator, and an analog integrator with a charge pump array to generate control signals that stabilize the output frequency and phase, reducing noise and PVT sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If an all-digital phase locked loop circuit is used to reduce area, then the semiconductor chip size is reduced, but the circuit becomes sensitive to PVT variations making precise control difficult
Solution Approach 1:
The patent applies local quality by using different circuit implementations for different functional blocks within the PLL. Specifically, the voltage controlled oscillator uses an analog implementation with switched capacitor circuits that are less sensitive to PVT variations, while other blocks can remain digital. This localized analog implementation in the VCO section provides better frequency control stability without requiring the entire circuit to be analog, thus maintaining area efficiency while improving reliability.
2Area of moving object
If a digital controlled oscillator is used in an all-digital PLL, then the circuit area is reduced, but the oscillator becomes sensitive to PVT variations
Solution Approach 1:
The patent substitutes a traditional digital controlled oscillator with an analog voltage controlled oscillator that uses switched capacitor technology. This replacement leverages analog circuit principles to achieve better frequency control precision. The VCO uses continuous voltage control rather than discrete digital steps, providing finer resolution and better linearity in frequency control, thereby improving manufacturing precision while maintaining a compact implementation suitable for integrated circuits.
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 provides a PLL circuit with improved performance and reduced costs by stabilizing the output frequency and phase, enhancing precision and reliability in semiconductor chips despite PVT variations.
Implementation Method 1
a charge pump array including a plurality of charge pumps and configured to output the control signal based on the pull-up and pull-down signals
Implementation Method 2
an analog integrator configured to output the control signal based on the first and second signals
Implementation Method 3
a voltage controlled oscillator configured to output an output signal based on the control signal
Implementation Method 4
a divider configured to divide the output signal by n and output the divided signal as the feedback signal
Data Source
AI summary
A phase locked loop circuit is provided which includes a bang-bang phase frequency detector configured to receive a reference signal and a feedback signal, detect a phase difference between the reference signal and the feedback signal, output a detection signal on the based on a result of the detection; an analog-digital mixed filter configured to receive the detection signal and output a control signal on the basis of the received detection signal; a voltage controlled oscillator configured to output an output signal in response to the control signal; and a divider configured to divide the output signal by n to output as the feedback signal. The detection signal is a digital signal, and the control signal is an analog signal.