USB Controller Automatic Clock Generation via PLLs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional USB controllers require external crystal oscillation or internal oscillator calibration to synchronize device and host clocks for real-time data transmission, leading to increased costs and calibration time.
Innovation Solution
A USB controller with automatic clock generation using a combination of oscillators, phase locked loops (PLLs), and a multiplexer to generate clocks without external crystal oscillation or internal calibration, synchronizing and filtering signals to meet USB specifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external crystal oscillation is used to synchronize USB device clock and host clock, then clock synchronization accuracy is improved, but production cost and PCB area increase
Solution Approach 1:
The patent extracts and eliminates the external crystal oscillator from the USB device, using only internal oscillation circuits. The system achieves clock synchronization by detecting host clock signals and generating device clock signals through internal PLL circuits, removing the need for expensive external crystal components while maintaining synchronization accuracy within USB specification limits.
Solution Approach 2:
The USB device performs self-calibration of its internal oscillation circuit by detecting the host clock signal and automatically adjusting its device clock signal through PLL circuits. This self-service mechanism eliminates the need for external calibration equipment and reduces production costs while achieving the required clock drift specifications.
2Measurement precision
If external crystal oscillation is used to synchronize USB device clock and host clock, then clock synchronization accuracy is improved, but PCB area increases
Solution Approach 1:
The patent removes the external crystal oscillator component from the PCB, significantly reducing the required PCB area. The system achieves clock synchronization functionality using only internal oscillation circuits and PLL circuits integrated within the USB controller, eliminating the need for additional external components and their associated PCB space.
3Area of stationary object
If internal oscillation circuit is used to generate USB clock, then PCB area is reduced, but calibration circuit and calibration time are required
Solution Approach 1:
The USB device performs automatic self-calibration by detecting the host clock signal and using PLL circuits to generate and synchronize device clock signals. This self-service calibration process eliminates the need for external calibration equipment and manual calibration procedures, significantly reducing calibration time while maintaining the benefits of using only internal oscillation circuits.
4Area of stationary object
If internal oscillation circuit is used to generate USB clock, then PCB area is reduced, but calibration circuit is required
Solution Approach 1:
The patent eliminates the need for separate external calibration circuits by integrating the calibration functionality directly into the USB controller's internal PLL circuits. The device uses its existing internal oscillation circuit and PLL mechanism to perform both clock generation and calibration functions, removing the need for additional dedicated calibration circuitry while maintaining PCB area reduction.
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
Rapid clock generation for USB controllers, reducing production costs and calibration time while ensuring accurate data transmission by eliminating the need for external crystal oscillation and internal oscillator calibration.
Implementation Method 1
a first phase locked loop (PLL), used for receiving the initial clock and outputting a controller operating clock having a first frequency
Implementation Method 2
by synchronizing the initial frame signal and filtering the jitter and noise by the third PLL so that the stabilizing frame signal conforms to the USB transmission specification
Data Source
AI summary
A USB controller with automatic clock generation comprising: an oscillating generator is used for generating an initial clock; a first phase locked loop is used for receiving the initial clock and outputting a controller operating clock having a first frequency; a controller is used for detecting at least one universal serial bus device and outputting an initial frame signal having a second frequency; a second phase lock loop is used for receiving the initial frame signal and outputting a sync frame signal having the first frequency; a third phase lock loop for receiving the sync frame signal and outputting a stabilizing frame signal having the first frequency; and a multiplexer is used for receiving the controller operating clock and the stabilizing frame signal and transmitting the controller operating clock or the stabilizing frame signals to the controller.