Internal Oscillator Frequency Trimming via On-Chip Processor
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Solution Overview
Problem
The existing frequency trimming process for internal precision oscillators (IPOs) in microcontroller integrated circuits is time-consuming and costly due to the need for external testers to measure and adjust oscillation frequencies, which limits production efficiency and increases the cost of microcontroller integrated circuits.
Innovation Solution
Implementing an internal frequency trimming method within the microcontroller integrated circuit, where a processor adjusts the trim value based on cycle counts from a general-purpose timer or software frequency counter, allowing the oscillator to calibrate its frequency autonomously and reducing reliance on external testers for decision-making and measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external testers measure and adjust oscillation frequencies during production testing, then frequency calibration accuracy is improved, but test time and production cost increase
Solution Approach 1:
The oscillator performs frequency calibration autonomously using an on-chip frequency counter and trim register, eliminating the need for external tester measurement and adjustment. The system self-measures its own frequency, self-determines the trim value, and self-adjusts the oscillation frequency through the trim register, thereby reducing test time while maintaining calibration accuracy.
Solution Approach 2:
The frequency measurement and decision-making functions are extracted from the external tester and transferred to on-chip components (frequency counter and processor). This extraction eliminates the time-consuming external measurement process while preserving the calibration accuracy by using dedicated on-chip measurement circuitry.
2Measurement precision
If external testers perform frequency measurement and decision-making, then frequency calibration accuracy is improved, but tester cost and complexity increase
Solution Approach 1:
The oscillator system performs its own frequency measurement and decision-making using on-chip components (frequency counter, processor, and trim register). This self-service approach eliminates the need for complex external tester equipment, reducing tester cost and complexity while maintaining calibration accuracy through dedicated on-chip measurement and control circuitry.
Solution Approach 2:
The measurement and decision-making functions are extracted from the external tester and implemented using simple on-chip components. This extraction reduces the complexity and cost of external testing equipment by transferring the intelligent functions to the device under test itself.
3Device complexity
If serial communication is used to transfer trim values, then device complexity is reduced, but communication speed and trimming efficiency decrease
Solution Approach 1:
The frequency counter, processor, and trim register are merged into a single integrated on-chip system. This integration eliminates the need for external communication interfaces and serial data transfer, enabling direct internal adjustment of the trim register and significantly improving communication speed and trimming efficiency while maintaining simple device architecture.
4Measurement precision
If external testers occupy serial ports during trimming, then measurement precision is maintained, but productivity of parallel tests decreases
Solution Approach 1:
The oscillator performs frequency measurement and calibration autonomously using on-chip components, eliminating the need to occupy external tester serial ports. This self-service capability allows the device to be calibrated independently, enabling parallel testing of multiple devices simultaneously and significantly improving productivity while maintaining measurement precision through dedicated on-chip measurement circuitry.
Solution Approach 2:
The frequency measurement function is extracted from the external tester and implemented using on-chip frequency counter circuitry. This extraction frees up external tester resources (serial ports) for other testing tasks, enabling parallel testing while maintaining measurement accuracy through dedicated on-chip measurement capabilities.
Data Source
AI summary
An internal precision oscillator (IPO) is trimmed within a microcontroller integrated circuit. The microcontroller integrated circuit receives a test program into flash memory on the microcontroller integrated circuit from a tester. The microcontroller integrated circuit also receives a reference signal from the tester. The IPO generates a clock signal having a frequency that depends upon a trim value. A general purpose timer on the microcontroller integrated circuit counts the number of cycles of the clock signal during a time period defined by the reference signal and outputs a digital value. A processor on the microcontroller integrated circuit executes the test program, reads the digital output, and adjusts the trim value such that the frequency of the clock signal is calibrated with respect to the reference signal. Test-time on the tester is reduced because the decision making during the frequency trimming process is made by the processor instead of the tester.