Crystal Oscillator Auto Calibration for Accurate Low-Power Clocking
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Solution Overview
Problem
High-speed wireline transceivers face challenges with accurate and stable clock signals, as external clock sources are expensive and increase device size and power consumption, while onboard clock generation also poses cost, size, and power consumption issues.
Innovation Solution
An integrated circuit device with dual clock paths for external and internal clock signal generation, including biasing circuitry and selector circuitry to choose between external and internal clock outputs, along with onboard clock generation using a frequency reference signal and variable loading capacitors calibrated by calibration circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external clock sources are used, then clock signal accuracy is improved, but device cost and power consumption increase
Solution Approach 1:
The system dynamically switches between external and internal clock paths based on operational mode. During calibration mode, the system uses the external clock path for high accuracy. During normal operation, it can switch to the internal clock path to reduce power consumption, making the clock source selection adaptive rather than static
Solution Approach 2:
The patent extracts only the essential frequency reference function from an external clock source, using a simple passive resonator instead of a full external clock generator. This reduces the power consumption and cost associated with external clock sources while maintaining the ability to achieve accurate clock signals when needed through selective activation of calibration modes
2Measurement precision
If external clock sources are used, then clock signal accuracy is improved, but device size increases
Solution Approach 1:
The patent extracts only the essential frequency reference function from an external clock source, using a simple passive resonator instead of a full external clock generator. This reduces the device size while maintaining the ability to achieve accurate clock signals when needed
Solution Approach 2:
The input terminal is designed to be universal, accepting both external clock signals and passive resonator signals through the same interface. This multi-functionality eliminates the need for separate external clock source components, reducing device size while maintaining flexibility in achieving accurate clock signals
3Ease of manufacture
If onboard clock generation circuitry is used, then device cost is reduced, but clock signal accuracy deteriorates
Solution Approach 1:
The system performs preliminary calibration using an external frequency reference signal to pre-adjust the variable loading capacitors before normal operation. This preliminary action ensures that the low-cost onboard clock generation circuitry achieves accurate clock signals without requiring expensive high-precision components
Solution Approach 2:
The calibration circuitry provides feedback adjustment to the variable loading capacitors based on the external frequency reference signal. This feedback mechanism enables the onboard clock generation to achieve accurate frequency output despite using cost-effective components, resolving the contradiction between cost and accuracy
4Use of energy by moving object
If onboard clock generation circuitry is used, then power consumption is reduced, but clock signal stability deteriorates
Solution Approach 1:
The system performs preliminary calibration using an external frequency reference signal to pre-adjust the variable loading capacitors before normal operation. This preliminary action ensures that the low-power onboard clock generation achieves stable and accurate clock signals during normal operation
Solution Approach 2:
The system dynamically switches between calibration mode (using external reference for stability) and normal operation mode (using onboard generation for low power consumption). This dynamic operation allows the system to achieve both low power consumption and stable clock signals by using the external reference only when needed for calibration
Data Source
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AI summary
An integrated circuit device having functional circuitry driven by a clock signal includes onboard clock generation circuitry. The clock generation circuitry includes an input configured to accept a frequency reference signal, at least one variable loading capacitor coupled to the input for converting the crystal resonator signal into a calibrated clock signal, and calibration circuitry configured to calibrate the at least one variable loading capacitor based on a reference voltage. The input configured to accept a frequency reference signal may be configured to accept a crystal resonator signal.