Auto-Adjusting Oscillator for Fast USB Clock Synchronization
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Solution Overview
Problem
Conventional Phase Lock Loops (PLL) and Delay Lock Loops (DLL) are not suitable for synchronizing an internal clock with a USB data stream due to long locking times and the lack of precision timing components, making them unsuitable for USB applications.
Innovation Solution
An auto-adjusting high accuracy oscillator with a frequency comparator, control tuning circuit, and oscillating element that uses successive-approximation methods to match the internal clock to a USB data stream within a 1% error rate, employing a frequency comparator to detect differences and a control tuning circuit to adjust the oscillating frequency, enabling the oscillator to adapt to any USB protocol specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Phase Lock Loops (PLL) or Delay Lock Loops (DLL) are used for synchronizing internal clock with USB data stream, then frequency matching capability is provided, but locking time becomes too long for USB applications
Solution Approach 1:
The patent applies preliminary action by pre-calibrating the oscillating element's frequency using a frequency comparator before actual USB data transmission begins. The system performs frequency measurement and adjustment in advance, storing the calibrated parameters for rapid deployment during operation, thereby eliminating the long locking time associated with conventional PLL/DLL approaches.
Solution Approach 2:
The patent replaces the mechanical feedback-based frequency adjustment mechanism of conventional PLL/DLL with an electronic frequency measurement and direct adjustment system. Instead of using phase detectors and voltage-controlled oscillators with long settling times, the system uses a frequency comparator to directly measure and adjust the oscillating element's frequency, significantly reducing the time required to achieve synchronization.
2Reliability
If precision timing components are used in conventional PLL/DLL approaches, then timing error prevention is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies self-service by enabling the oscillating element to automatically measure and adjust its own frequency using the frequency comparator and control tuning circuit. The system performs self-calibration without requiring external precision timing components, thereby maintaining timing accuracy while reducing device complexity and eliminating the need for additional precision components.
Solution Approach 2:
The patent implements a feedback mechanism where the frequency comparator continuously monitors the oscillating element's frequency and feeds back adjustment signals to the control tuning circuit, which in turn adjusts the oscillating element. This closed-loop feedback system ensures timing accuracy without requiring external precision timing components, replacing them with an integrated self-regulating feedback mechanism.
3Measurement precision
If conventional PLL/DLL approaches are used, then frequency synchronization capability is achieved, but the system cannot be adapted to different USB protocol specifications
Solution Approach 1:
The patent applies dynamics by making the oscillating element's frequency adjustable and reconfigurable through the control tuning circuit. The system can dynamically change its operating frequency and characteristics to match different USB protocol specifications (such as USB 1.1, USB 2.0, and future variants), providing both frequency synchronization accuracy and protocol adaptability through programmable frequency control.
Solution Approach 2:
The patent implements universality by designing the oscillating element and control tuning circuit to work across multiple USB protocol specifications. The frequency comparator and control mechanism are configured to accommodate different frequency requirements and protocol characteristics, making the system universally applicable to various USB standards without requiring separate dedicated circuits for each protocol.
Data Source
AI summary
An auto-adjusting high accuracy oscillator is disclosed, which comprises: a frequency comparator, for comparing a synchronization signal obtained from a USB host with an oscillation signal obtain from a device; a control tuning circuit, further comprising a counter and an adder/sub circuit; and an oscillating element; wherein a variation is obtained by the counting of the counter while transmitting the variation to the adder/sub circuit to be encoded thereby into a digital code so as to enable the oscillating element to perform a frequency up/down operation accordingly for approaching the synchronization signal successively.