Calibrating Internal RC Oscillator Clock Signal Without Crystal
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Solution Overview
Problem
Electronic devices, such as EPD drivers and authentication tokens, require precise clock signals but face challenges with high variability in internal RC oscillators, making it difficult to achieve the necessary precision due to semiconductor process variations, especially when external quartz crystals are not feasible due to space or cost constraints.
Innovation Solution
A method is implemented where an electronic device generates a high-speed clock signal that is communicated to an external calibration system for measurement, allowing for the calculation and application of calibration values to produce a precise clock signal, such as a 32.768 KHz frequency, by dividing a high-speed reference signal using a processor and external programming/calibration station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external quartz crystal oscillator is used to generate a precise clock signal, then the clock signal accuracy is improved, but the device size and cost increase
Solution Approach 1:
The patent extracts the clock signal generation function from the traditional external crystal oscillator and relocates it inside the processor as an internal RC oscillator. This eliminates the need for external crystal components while maintaining the clock signal generation capability, thereby reducing device size and integration complexity.
Solution Approach 2:
The patent merges the clock signal generation function with the processor by integrating an internal RC oscillator directly into the processor chip. This consolidation eliminates separate external crystal oscillator components and reduces the overall device footprint while providing the necessary clock signals for processor operation.
2Measurement precision
If an external quartz crystal oscillator is used to generate a precise clock signal, then the clock signal accuracy is improved, but the power consumption increases
Solution Approach 1:
The patent extracts the clock signal generation function from the power-hungry external crystal oscillator and relocates it to a low-power internal RC oscillator integrated into the processor. This extraction eliminates the need for external crystal components while maintaining the clock signal generation capability, thereby reducing device size and integration complexity.
Solution Approach 2:
The patent employs a low-cost, low-power internal RC oscillator that consumes significantly less power compared to external crystal oscillators. While RC oscillators have lower inherent accuracy, the combination of internal generation with post-correction techniques provides sufficient precision for the application while dramatically reducing power consumption, making it suitable for battery-powered devices.
3Area of stationary object
If an internal RC oscillator is used to generate a clock signal, then the device size and power consumption are reduced, but the clock signal accuracy deteriorates due to process variations
Solution Approach 1:
The patent implements a feedback mechanism where the actual clock signal frequency generated by the internal RC oscillator is measured and compared against the target frequency. Based on this feedback, a correction factor is calculated and applied to adjust the RC oscillator's output, thereby compensating for process variations and improving clock signal accuracy while maintaining the benefits of internal integration.
Solution Approach 2:
The patent changes the operating parameters of the internal RC oscillator through post-correction techniques. By adjusting the oscillator's frequency characteristics based on measured performance and applying calibration factors, the system compensates for manufacturing process variations and achieves the required clock signal accuracy despite using an internal RC architecture instead of an external crystal.
Data Source
AI summary
A method is used in calibrating an internal clock generator. An electronic device is instructed to output a high-speed clock signal which is communicated to an external calibration system. The high-speed clock signal is measured using measurement equipment associated with the external calibration system. One or more calibration values based on the measured clock signal value are calculated. The calculated calibration values are communicated to the electronic device. The electronic device is instructed to generate a calibrated clock signal by applying the one or more calibration values to an internally generated clock signal.