Oscillator Calibration Using a Fast Clock Reference
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Solution Overview
Problem
Calibrating slower oscillators in driver ICs for mobile devices is time-consuming and increases test costs due to semiconductor process variations.
Innovation Solution
An oscillator calibration apparatus and method that uses a calibrated faster-frequency oscillator to calibrate a slower-frequency oscillator, comprising a counter, comparator, and adjusting unit to generate and apply calibration signals, allowing the slower oscillator to be calibrated each time the device is powered on.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the slower oscillator is calibrated using traditional methods, then the calibration accuracy is improved, but the calibration time is increased and test cost is increased
Solution Approach 1:
The patent introduces a counter as an intermediary device that counts the cycles of the slower oscillator signal within a fixed time period defined by the faster oscillator. This counter provides a quantitative measurement of the slower oscillator's frequency deviation, enabling accurate calibration without time-consuming direct measurement methods. The counter acts as a mediator between the two oscillators, translating frequency differences into countable values.
Solution Approach 2:
The patent uses the faster oscillator as a reference copy or standard against which the slower oscillator is measured. By comparing the slower oscillator's output against the known accurate frequency of the faster oscillator over a fixed number of cycles, the system creates a reference framework that enables quick and accurate calibration without requiring external calibration equipment or time-consuming procedures.
2Measurement precision
If the slower oscillator is calibrated in factory, then the calibration accuracy is improved, but the test cost is increased
Solution Approach 1:
The patent implements a self-calibration mechanism where the driver IC uses its own faster oscillator (which serves as an internal reference) to automatically calibrate its slower oscillator. This self-service approach eliminates the need for external calibration equipment and factory calibration processes, significantly reducing test costs while maintaining calibration accuracy. The system calibrates itself using resources already available within the device.
Solution Approach 2:
The faster oscillator serves multiple functions: it acts as the normal operating clock for the driver IC and simultaneously serves as the reference standard for calibrating the slower oscillator. This multi-functionality eliminates the need for separate calibration equipment or processes, reducing manufacturing complexity and test costs while maintaining calibration accuracy.
Data Source
AI summary
An oscillator calibration apparatus includes a counter, a comparator and an adjusting unit. The counter is utilized for receiving a first clock signal and a second clock signal, and utilizing the first clock signal to sample the second clock signal to generate at least one counting value, where the first clock signal is generated from a first oscillator, and the second clock signal is generated from a second oscillator different from the first oscillator; the comparator is coupled to the counter, and is utilized for comparing the counting value with a predetermined value to generate at least one calibration signal; and the adjusting unit is coupled to the comparator, and is utilized for adjusting a frequency of the second oscillator according to the calibration signal.